Climate emergencies

INTRODUCTION — This topic provides information and recommendations geared to reducing harms related to exposures from heat, wildfires, floods, and hurricanes.

Exertional heat illness, heat stroke, and heat-related illnesses (eg, heat syncope or heat exhaustion) are covered elsewhere:

●(See "Heat stroke in children".)

●(See "Heat illness (other than heat stroke) in children".)

●(See "Severe nonexertional hyperthermia (classic heat stroke) in adults".)

●(See "Exertional heat illness in adolescents and adults: Management and prevention".)

Other health effects of air pollution are discussed separately:

●(See "Occupational and environmental risks to reproduction in females: Specific exposures and impact", section on 'Reproductive impact'.)

●(See "Overview of possible risk factors for cardiovascular disease", section on 'Air pollution'.)

●(See "Increasing prevalence of asthma and allergic rhinitis and the role of environmental factors", section on 'Air pollution'.)

●(See "Risk factors for asthma", section on 'Air pollution'.)

Further information on caring for patients in disasters is provided elsewhere:

●(See "Disaster settings: Care of gynecologic problems".)

●(See "Disaster settings: Care of pregnant patients".)

IMPACT OF CLIMATE CHANGE — Human-caused global climate change is a result of rising atmospheric concentrations of greenhouse gasses primarily due to the burning of fossil fuels. Climate change is associated with more frequent and intense heat waves, a longer and more destructive hurricane season, greater flood and drought risk, and a lengthened fire season with more severe and frequent wildfires, especially in drought-prone areas [1-4]. These and other effects of climate change have contributed directly to adverse health effects, increased the burdens of communicable and noncommunicable diseases, and compromised health care delivery [5,6].

HEAT

Adaptation to heat — The body has four mechanisms to remove heat: conduction, convection, evaporation, and radiation. When ambient temperature exceeds body temperature, sweating (evaporation) is the predominant means to dissipate heat. Humid air reduces the ability of sweating to remove heat from the body. When heat stress exceeds the body's ability to compensate (eg, through increased sweating), access to indoor or outdoor cooling is necessary to avoid heat-related illnesses and exacerbations of medical conditions.(See 'Cooling options' below.)

Who is at risk? — Physiologic adaptive capacity to heat exposure declines with advanced age (especially over 80 years) and is affected by medical conditions and prescription medications (see 'Risk factors for heat related illness' below). Exposure to warm weather, even temperatures known locally as not particularly hot, can result in excess morbidity and mortality in at-risk groups [7,8].

In young, healthy persons, thermoregulatory homeostasis fails at a wet-bulb temperature (a measure of heat stress and efficiency of cooling by evaporation in direct sunlight) of 31°C (88°F) at 100 percent humidity or 38°C (100°F) at 60 percent humidity [9]. However, the observed temperature and humidity mortality thresholds worldwide are far lower than what are seen in healthy, young subjects. For example, in Boston, Massachusetts, mortality from heat exposure begins to rise with an average daily temperature of around 22ºC (72ºF) [10]. An estimated 30 percent of the human population lives where temperature and humidity exposures are extreme enough to result in excess mortality for at least 20 days of the year. With climate change, 50 to 75 percent of all people may live with such conditions within this century [11]. Heat illness risk based on heat index and wet-bulb temperature are shown in the tables (table 1 and table 2 and table 3).

Risk factors for heat related illness

Chronic conditions — Several medical conditions, as well as older age, are associated with greater heat-related morbidity and mortality. These include diabetes mellitus, cardiovascular disease, chronic obstructive lung disease and asthma, chronic kidney disease, mental health disorders, dementia, and pregnancy [12-19]. (See 'Disease-specific considerations' below.)

Medications — Several classes of medications are associated with an increased risk of hospitalization in warmer months or with exposure to heat, including angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), beta blockers, diuretics, antipsychotics, and selective serotonin reuptake inhibitors (SSRIs) (table 4) [20-22]. In addition, extreme heat exposure may cause certain medications to lose efficacy and some medication delivery devices may malfunction. Temperatures inside cars, including car glove compartments and trunks, and mailboxes may reach extreme temperatures even when ambient temperatures are not exceptionally high. These exposures may be particularly relevant for medication delivery devices. As examples, intramuscular epinephrine and inhaled albuterol delivery devices may deliver lower medication doses or no dose at all with extreme heat exposure [23,24].

Biologic and social determinants — Basic demographics and a social history can uncover additional risks for heat-related morbidity and mortality. Elevated risk has been found in:

●Males, who tend to be at greater risk, perhaps partially due to likelihood of outdoor work or other exposures [25]

●Older adults [25]

●Infants and young children

●Outdoor workers (eg, agriculture, firefighting, construction, roofing) [26]

●Athletes, either outdoor, or indoor if buildings are inadequately cooled. High school and college football players may be at greatest risk [27]

●Persons who cannot access or afford adequate air conditioning [28,29]

●Socially isolated persons who do not have someone to contact or check in on them during extreme heat [28]

●Persons with limited mobility who have difficulty accessing transportation to cooling centers

●Persons who are less well physiologically and behaviorally adapted to hot conditions because they reside in cooler regions with fewer hot days during the warm season

●Persons living in urban heat islands where dark, heat-avid surfaces predominate, and tree canopy and vegetation are sparse

Managing heat risk

Assessing individual heat exposure — Clinicians can assess risk for heat exposure based upon temperature forecasts for their location. These forecasts are typically accurate enough three or more days in advance of a heat event. However, they may not accurately assess individual heat exposure for all persons. As an example, temperatures are often reported for entire cities based upon measurements at a single location. These reports may misrepresent an individual's heat exposure since temperature variance in cities can exceed 20°F due to differences in heat retention across urban landscapes [30]. Temperature gradients across floors of buildings can also be large, with upper floors having temperatures much hotter than lower floors.

Heat alerts — Heat warnings of weather that may increase risk of harm from heat exposure are issued by national weather services in many countries. They are the most visible alert for many people and can be accessed on smartphones, television news channels, and the radio. These alerts are typically triggered when a metric of heat (usually the heat index in the United States) is forecast to surpass a threshold. However, the threshold for a heat alert cannot account for variable exposure or sensitivity to heat and is often set well above temperatures at which increased rates of hospitalizations occur [31]. In addition, these alerts are given only a day or two before heat events occur for entire cities and so leave little time to prepare.

Resources to better identify hazardous heat events are available in certain areas. Health-based heat ranking systems, akin to those known for hurricanes, that categorize heat forecasts based upon their potential to exact excess morbidity and mortality are in use in several cities in the United States (eg, Miami, Los Angeles, Kansas City, Milwaukee, and Madison) and other cities globally. In addition, services are available to push notifications to hospitals and clinics several days in advance of heat events that pose risks to health.

Guidance to patients regarding heat exposure — Patients with medical conditions or other risk factors that increase their sensitivity to heat should receive guidance in advance of heat events that may lower their risk of harm from heat exposure. Guidance should focus on the following, which is also applicable to healthy persons:

●Accessing weather forecasts from a reliable source such as the National Weather Service, a local media outlet, or The Weather Channel website.

●Measuring temperatures inside the home with a thermostat or thermometer.

●Identifying temperatures that pose health risks based upon an assessment of disease severity, medications, age, occupation/hobbies, and social determinants as identified above (see 'Biologic and social determinants' above). Location specific heat alerts for municipal areas in the United States that are delivered when heat is likely to cause excess morbidity or mortality can be accessed at no cost.

●Assessing hydration status, including by using a urine hydration chart.

●Maintaining adequate hydration by adequate fluid intake. Avoiding sugary drinks, alcohol, and caffeine.

●Reviewing medication use, including over-the-counter medication use (eg, nonsteroidal anti-inflammatory drugs [NSAIDs]), to assess for potential to increase risk of harm for heat exposure and/or dehydration (table 4). (See 'Medications' above.)

●Scheduling outdoor activities when temperatures are lower, usually before 11 AM or after 6 PM, even if a heat warning hasn't been issued.

●Wearing loose-fitting, lightweight, and light-colored clothing. Wearing sunscreen and a hat when outside.

●Planning for cooling options in case indoor or outdoor temperatures exceed safe limits. (See 'Cooling options' below.)

●Wearing footwear that will protect your feet from hot surfaces, especially for patients with diabetic neuropathy.

Cooling options

●Fans – Fans can increase heat removal from the body even at relatively high temperatures. The WHO recommends avoiding fan use at temperatures above 35ºF. However, fans have been found to be safe, and potentially beneficial, in healthy young adults (age 18 to 40) and healthy older adults (age >65) at temperatures below 39ºC/102ºF and 38ºC/100ºF respectively. For older adults (age >65) on anticholinergic and other medications that impair sweating, fans may be safely used at temperatures below 37ºC/98ºF [32]. Using a fan when temperatures are above approximately 45 C/110 F with dry air (<10 percent relative humidity) has been shown to increase heat uptake in healthy, young males.

For persons who are over 80 or pregnant, especially those with chronic medical conditions (including obesity, cardiovascular, respiratory, neurologic, psychiatric, autoimmune, renal, oncologic, metabolic or infectious) and/or who take medications that affect water balance or thermoregulation (table 5), temperatures at which fan use may increase heat uptake in the body may be lower than those specified above.

●Air conditioning – Patients who have access to the use of reliable and affordable air conditioning in their home can be protected from heat extremes. In the United States, funding to offset electricity costs from air conditioning is being made available through the United States Federal Government Low Income Home Energy Assistance Program (LIHEAP) program, which is administered by states.

For patients who have window air conditioning units, they should ideally have them installed in the room in which they sleep. Health-status and age-specific safe indoor temperature thresholds have not been established. Some expert bodies recommend keeping indoor temperatures below approximately 28 C/82 F [33], though these thresholds are not informed by health-based outcomes research.

●Public cooling centers, splash pads, and pools – Many cities open cooling centers during heat events and may extend hours at public pools and splash pads, and public transportation fares may be waived. Cooling centers can provide safe cooling spaces, but their efficacy may be limited. They may only be opened when the National Weather Service declares a heat warning that may be at temperatures above those that pose risks to patients. They also may be difficult to access for patients with limited mobility or lack of familiarity with or knowledge of the site. Lastly, at-risk patients may have to stand outside in the heat for prolonged periods waiting for public transit on hot days.

●Other places to cool off – As alternatives to cooling centers, accessing neighbors' homes may be a more accessible and equally safe alternative. Places of worship, libraries, and neighborhood-based organizations may not only provide safer indoor temperatures but also a community that can reach out to at-risk individuals. Tree shade can markedly decrease ambient temperature. Local parks may be more accessible and familiar than cooling centers and should be considered as options in formulating a heat plan.

Disease-specific considerations

●Diabetes – Heat events pose a greater threat to patients with diabetes due to an alteration in the body's ability to adapt to heat [34]. Specifically, the ability to dissipate heat through sweating and vasodilation is impaired, especially in settings of poor glycemic control [35].

For insulin-dependent diabetics, heat may change insulin requirements. During heat events, the need for blood glucose monitoring may need to be increased. Plans for adjustment of insulin during heat events can be established during routine care visits, ideally before the onset of the warm season. In addition, heat can damage glucometers, insulin pumps, test strips, and other diabetes equipment and supplies; they should not be left in a hot car, by a pool, in direct sunlight, or on the beach. Diabetic neuropathy may increase risk of burns, especially to feet, and patients should be cautioned against going barefoot. Diabetics with autonomic neuropathy may be especially at risk for heat-related morbidity and mortality due to impaired homeostatic responses to heat stress.

●Chronic obstructive pulmonary disease and asthma — Heat can increase ground level ozone formation, which can trigger asthma and chronic obstructive pulmonary disease (COPD) flares. During hot weather, individuals with COPD and asthma should be advised to check the local air quality index (AQI) (see 'Identifying exposure to harmful air quality' below). Should the AQI be above 50, a plan informed by an individual's disease severity and options for accessing cleaner air should be made. Exposure to hot air also increases bronchoconstriction [12].

●Mental health disorders — Higher temperatures are associated with increased rates of suicide, aggression (including intimate partner violence), and substance use [15]. In addition, persons with mental health disorders are also at high risk for morbidity and mortality during heat waves [7,15,36,37].

●Dementia — Persons with dementia or other cognitive impairment may need assistance with assessing temperatures, staying hydrated, and accessing cooling resources.

●Pregnancy — Higher ambient temperatures are associated with a low birth weight, stillbirths, preterm birth, and congenital anomalies, including congenital cataracts, hypospadias, and certain types of cardiac and neural tube defects [14,38].

●Cardiovascular disease — Heat exposure has been associated with elevated risk of morbidity and mortality from myocardial infarction, stroke and heart failure and may promote atrial and ventricular arrhythmias [17,39]. Many patients with cardiovascular disease have comorbid conditions, such as diabetes, and take medications, such as diuretics, ACEIs/ARBs, or beta blockers, that may further increase risk of harm during heat exposure.

●Chronic kidney disease — Kidney disease is one of the most commonly identified contributors to excess morbidity and mortality during heat events. A multinational meta-analysis found a 1ºC (approximately 0.6ºF) temperature increase may elevate risk of kidney failure by 1.1% (95% CI: 0.9-1.3) and mortality from kidney disease, including kidney failure, urolithiasis, acute kidney injury (AKI), and urinary tract infection, by 3.1% (95% CI: 0.5-5.8) [40]

Formulating a heat plan — An effective heat plan includes how to access weather forecasts, tips for staying safe, and a plan for how to stay cool when it gets hot. Ideally, these are developed collaboratively between patient and provider and are tailored to specific medical concerns and preferred resources available to the patient (eg, cooling center versus a neighbor's home). Such clinical resources, including sample heat action plans and guidance for their completion, as well as disease-specific heat tip sheets for patients are available from Americares.

WILDFIRES

Changing wildfire exposure — Wildfire smoke has far-reaching impacts, affecting people who are far away from the fires themselves. Between 2008 and 2012, nearly 30 percent of the United States population lived in areas with moderate exposure to wildfire smoke [41]. Communities without much experience with wildfires, especially those that are adjacent to currently wildfire prone areas, may be increasingly at risk for wildfire events.

Wildfire smoke can affect communities far from the source. As an example, in June 2023, smoke from wildfires in Canada drifted hundreds of miles to New York City, resulting in increased ambient fine particulate matter (PM_2.5) [42]. During smoke waves, citywide daily mean PM_2.5 levels reached 100.9 μg/m³ (reference, 9.0 μg/m³). During these periods, emergency department visits for asthma in both pediatric and adult patients increased to 261 per day (reference, 181.5 per day), and were increased compared with nonsmoke periods (incidence rate ratio 1.44, 95% CI 1.31-1.58).

Wildfire health impact — Wildfires have many immediate and direct health effects including burns and physical trauma. They also create conditions favorable to landslides as they burn through vegetation that stabilizes soils. Living through a wildfire has been shown to result in protracted health effects, especially for mental health, with survivors showing higher rates of depression, substance abuse, and posttraumatic stress disorder up to a decade later [43]. Childhood survivors of wildfires also have been found to have persistent mental health effects into adulthood [44].

Smoke is the most important health risk from wildfires, and contains many toxicants based upon what gets burned (eg, lead in car batteries) and often includes acrolein (lung irritant), polyaromatic hydrocarbons (carcinogens and neurotoxicants), oxides of nitrogen (lung irritant and ozone chemical precursor), and particulate matter (PM). In the United States, wildfire PM less than 2.5 microns in diameter (PM_2.5) is associated with an estimated 6300 deaths and between 1300 and 5900 emergency department visits per year [45].

Populations at increased risk — The airborne toxicants in wildfire smoke contribute to excess population-wide morbidity and mortality but have particular relevance to specific populations, such as those with respiratory, cardiovascular or kidney disease.

●Asthma, COPD, and other chronic respiratory diseases – Wildfire smoke causes an increase in breathing difficulties and respiratory symptoms (eg, coughing, wheezing, and chest tightness) as well as greater medication usage, emergency department visits, and hospital admissions [46-48].

●Cardiovascular disease – Persons with cardiovascular disease experience greater incidence of ischemic events, worsening of heart failure and arrhythmias, as well as greater emergency department visits, hospital admissions, and mortality from CVD [49,50].

●Chronic kidney disease – Wildfire smoke exposure results in excess same-day mortality for dialysis patients, decreased renal function, and progression to end-stage renal disease [51,52]. Fine particulate matter (PM_2.5) damages the kidney through several mechanisms, including oxidative stress, inflammation, triggering apoptosis, DNA damage, and autophagy [53].  

●Other risk factors – Wildfire smoke exposure may be particularly dangerous for older adult individuals with decreased lung function and young children with lower pulmonary reserves [54,55]. Persons with physical disabilities may face barriers to evacuating to safety and/or implementing protections. Outdoor workers and persons unable to relocate face obstacles to lowering their exposures to wildfire smoke [56].

The effect on of air pollution on female reproductive health is discussed separately. (See "Occupational and environmental risks to reproduction in females: Specific exposures and impact", section on 'Air pollution'.)

Managing wildfire risk

Identifying exposure to harmful air quality — Identification of fire risk and hazardous air quality is necessary to identify when additional steps need to be taken. Fire-related air quality conditions for United States locations can be found at AirNow's Fire and Smoke Map, and forecasts for future air quality conditions can also be found at AirNow.

Most smartphone weather apps include the air quality index (AQI). The AQI is an assessment of air quality based upon five pollutants: particulate matter (PM), ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The higher the number, the worse the air quality (table 6) [57].

Masking while outdoors — Masks labeled N95 (United States), FFP2 (Europe), KN95 (China), P2(Australia/New Zealand), DS2 (Japan), PFF2 (Brazil), and KF94(Korea) should filter a large proportion of solid (but not gaseous) components of wildfire smoke.

Masks come in different sizes and must fit well to filter pollution [58]. Children younger than two years of age should not wear a mask. Air leaks around masks that are not properly fitted or worn dramatically reduce protection from PM and other pollutants. As consistent proper mask fit may not be readily achieved for many persons, time spent outdoors during periods of poor air quality (eg, AQI >100) should be limited even when an appropriate mask is available.

Management of indoor air quality — During periods of compromised air quality (eg, AQI >50), many authorities recommend staying indoors. However, indoor air quality may be comparable or, in some instances, worse than outdoor air quality. If a person is staying indoors, it is important to maintain good indoor air quality.

●Reducing indoor pollution – Common sources of indoor air pollution include smoking, vaping, wood fires, candles, incense, and cleaning products. Cooking can also release air pollutants. Natural gas stoves, especially older ones, release carbon monoxide and oxides of nitrogen. Exhaust hoods should be used with gas stoves regardless of what is being cooked. If a hood is not available, windows or doors should be opened to allow for ventilation.

●Indoor air filtration – Homes with forced air heating and cooling typically have replaceable air filters in their air handlers. These filters are given a minimum efficiency reporting value (MERV) rating. The higher the rating, the more effective the filters are at reducing air pollutants. Only MERV 13 and higher, or a high-efficiency particulate air (HEPA) filter, will substantially remove PM_2.5.

Although few residential ventilation systems can accommodate a HEPA filter, portable air filters, designed for use in individual rooms, may have HEPA filters. Their ability to reduce air particle concentrations depends on their size, the fan speed, the area to be cleaned, the filter efficiency (ie, MERV rating).

Low-cost portable air filters can be made with a box fan, a MERV filter (ideally MERV 13 or higher), and some bungee cords or tape. A simple example of such a do-it-yourself filter can be found in the figure (figure 1).

●Creating a clean room – Creating a clean room in a home should be completed before wildfire smoke appears. It involves many of the steps above:

•Find a room that can fit all the people living in the home, ideally, with air conditioning

•Seal it by closing windows and doors

•Filter the air using a built-in filter in a heating, ventilation, and air conditioning (HVAC) system or a portable air filter with the capacity to filter the room.

Wildfire action plans — Harm from wildfire and smoke exposure can be mitigated through advanced planning. A wildfire action plan should include:

●Guidance on how to access air quality information (eg, AirNow)

●Guidance on actions to take at specified AQI levels

●Contingency plans for power outages (see 'Power outage planning' below)

●An evacuation plan, including identification of an evacuation route and meet-up location

Ideally, these plans are developed collaboratively between patient and provider and are tailored to specific medical concerns. Resources for creation of a wildfire action plan and resources for patients are available from Americares.

Many individuals may be unwilling to evacuate even when wildfire risks are imminent and dire [59]. Assessing willingness to evacuate should form a basis for wildfire action plans for at-risk patients. Individuals may not appreciate certain risks from wildfires such as power outages, which can make electricity-dependent medical devices (eg, continuous positive airway pressure machines) inoperable, and water shortages, which result from failures of electric well pumps (see 'Power outage planning' below). Should individuals express reluctance to evacuate, a focus on risk reduction (eg, indoor air quality filtration, removal of flammable materials and vegetation around the home) should be prioritized.

HURRICANES AND FLOODS

Changing hurricane and flood exposure — Climate models project more intense hurricanes and associated coastal flooding and wind damage in the future. Hurricane peak intensity has been occurring closer to shore, and in the United States, atlantic hurricane tracks have been shifting northward, putting more northern coastal areas, which may have less investment in preparedness, at greater risk from hurricane strikes [60,61]. Climate change is also increasing the frequency of heavy precipitation events and associated flooding, especially in low-wealth communities [62].

Hurricane and flood risks to health — Like wildfires, hurricanes and floods have immediate and prolonged health risks. Immediate risks include unintentional injuries such as drowning, electrocution, lacerations, falls, head injuries from falling debris, and motor vehicle accident trauma.

A broad array of disease burdens and specific risks to persons with specific conditions have been associated with floods and hurricanes that can transpire over days to years after the event. These include:

●All-cause mortality, as well as cardiovascular and respiratory deaths, increased after a flooded day in 761 communities worldwide, and this risk persisted for up to 60 days [63]. Up to 0.41 percent of respiratory deaths, 0.18 percent of cardiovascular deaths, and 0.10 percent of all-cause deaths were attributed to floods. The risks varied by local climate type and were greater in areas with lower socioeconomic status, less human development, or higher proportion of older residents. These deaths include those caused by direct physical forces and hazards related to the flood as well as those related to additional factors such as limited access to and contamination of food and water, decreased access to healthcare, and increased exposure to pathogens.

●Mortality from respiratory diseases has been found to increase 8.3 percent one month after hurricanes [64]. This may result from disruption in care access, exposure to molds or air pollution that trigger flares of COPD, or respiratory infections.

●Myocardial infarctions and strokes were 22 and 7 percent higher, respectively, in areas more severely affected by Hurricane Sandy [65]. Increased exposure to air pollution (eg, dust mobilized by high winds) increases physical workload (eg, removing debris) and psychological distress [66].

●In persons with type 2 diabetes, emergency room visits increased 84 percent during the week of Hurricane Sandy [67] In addition to concerns directly related to diabetes, such as skin ulcers and prescription refills, diabetics may be more likely to seek care in emergency departments after hurricanes due to comorbid conditions such as myocardial infarction, hypertension, renal failure, and drug dependence [68].

●Patients on dialysis have elevated mortality after hurricanes and may be more likely to need emergency department care, be hospitalized, and receive dialysis during hospitalization [69,70].

●Preterm birth and low birth weight are more common after hurricanes [71] and offspring may be at greater risk for mental health disorders [72]. Evidence suggests that adverse birth outcomes may be due to closure of care sites, including pre-emptively in advance of hurricanes, as well as from the stress of the storms on pregnant people [73,74].

●Prolonged disaster declarations have been associated with greater mortality in cancer patients probably due to compromised care access [75].

●Post traumatic stress disorder (PTSD), depression, and anxiety symptoms have been documented after hurricanes, with prevalence varying with the intensity of the storm or flood. Symptoms may persist for years after these events. Children, females, older adults, and persons in certain occupations, such as farm workers and first responders (eg, emergency medical personnel, police officers, and fire fighters), may also be more at risk [76-79].  

●Mental health symptoms after exposure to a hurricane are associated with lack of necessities, including medications and access to medical care, personal physical exposure to hurricane forces (eg, wind, rain, storm surge), evacuation, loss of a loved one or pet, repeat exposure to hurricanes, existing mental health disorders, or recent personal adversity [80-82].  

Toxic exposures — Industrial, wastewater, and agricultural sources can release hydrocarbons, volatile organic compounds, and heavy metals into surrounding water and soil. Infrastructure failures contribute to carbon monoxide poisonings from poorly ventilated generators and makeshift heating measures. Gasoline shortages after Hurricane Sandy led to gasoline siphoning-related toxidromes.

Managing hurricane and flood risk

Monitoring hurricane and flood forecasts — A "hurricane watch" indicates that hurricane conditions (winds of greater than 74 mph) are possible. A "hurricane warning" indicates that hurricane conditions are expected. Hurricane warnings are given 36 hours prior to the expected hurricane impact to give residents time to prepare or evacuate.

Flood forecasts are less certain than hurricane forecasts as flood risk depends on many factors aside from absolute rainfall, including geography, volume of recent rainfall, the built environment, and proximity to rivers (and their levels). The National Weather Service does provide flash flood forecast maps that show where flooding may be most likely given expected precipitation.

Delivering guidance to patients regarding hurricanes and floods — Preparing for floods and hurricanes centers on assessment of risk from forecasts and preparedness measures. Patients with significant chronic medical concerns, limited access to transportation, and smaller social networks, among other factors, may be more vulnerable to harm. These patients should receive guidance focused on:

●Preparing for advancing hurricanes

•Prepare an emergency supplies kit, which should include a list of all medications, doses, and any allergies, as well as contact information for key medical providers.

•Contingency plans for power outages should be based on medical conditions and treatments. (See 'Power outage planning' below.)

•Prevention of injuries from shattered glass and flying objects, including boarding windows with storm shutters or plywood and securing movable outdoor items.

●Staying safe during hurricanes

•Pay attention to local advisories and warnings before, during, and after the storm.

•Shelter in a designated storm shelter or interior room.

•Turn off power to homes with standing water inside.

●Keeping safe after hurricanes or floods

•Avoid walking or driving in flooded areas.

•Avoid consuming any food or water that has contacted flood water.

•Avoid re-entering damaged homes or buildings without prior inspection by an authority.

•Avoid using wet electrical devices.

•Avoid using stoves, ovens, or other appliances that use combustible fuels for heating as they can cause carbon monoxide poisoning.

•Follow local guidance on drinking water safety and consumption.

•Follow the Centers for Disease Control and Prevention guidance if entering or cleaning a flooded building. Patients with asthma or who are immunosuppressed should avoid re-entering flooded buildings until cleanup has finished.

●Developing an evacuation plan – An evacuation plan should include:

•Identification of an evacuation route and meet-up location.

•Backup locations to receive medical treatment (eg, dialysis)

Responsiveness to evacuation alerts has been found to vary among individuals. Men and full-time residents may be more likely to want to stay and protect their property, whereas homes with children, older adults , pregnant persons, individuals with health concerns, or part-time residents are more likely to evacuate early [83].

For individuals with chronic medical conditions or who rely on electronic devices such as ventilators, reviewing the risks from hurricanes and floods may be helpful to enable evacuation to safety when necessary.

If a high-risk patient will not have the needed assistance to evacuate, a provider can ask permission to share the patient's contact information with local emergency managers.

Extensive, multilingual guidance on evacuation planning is available from Ready.gov.

Resources for creation of a hurricane and flood action plan and resources for patients are available from Americares.

POWER OUTAGE PLANNING — Heat waves, wildfires, floods, and hurricanes contribute to many power outages in the United States. Power outages have been found to jeopardize health, especially for persons with chronic medical conditions [84]. Persons who rely on electrically powered medical devices may be particularly at risk. Power outages also may compromise access to water, especially for private well-dependent households.

Contingency plans for power outages should include:

●Identification of medical condition-specific risks from power outages (eg, refrigerated medication needs, ventilators, assisted ambulation, etc)

●Plans for availability of backup power generation and/or backup batteries as needed

●Persons with lifesaving, electricity-dependent care devices such as ventilators should have the battery duration of their devices assessed and used to inform planning for backup power needs

●Potable water stockpiles if patient relies on an electric pump for well water

●Heating and/or cooling plans

Patients should be advised of carbon monoxide poisoning risks with the use of generators, as well as other devices that combust fuels indoors. (See "Carbon monoxide poisoning", section on 'Sources of exposure'.)

SUMMARY AND RECOMMENDATIONS

●Impact – Climate change is changing the location, intensity, and frequency of extreme events such as heat waves, hurricanes, floods, and wildfires. These extreme events create foreseeable and preventable disease burdens and unique health risks to individuals with chronic medical conditions. (See 'Impact of climate change' above.)

●Heat exposure – Heat exposure that creates excess morbidity and mortality for many patients is already common, even at temperatures not typically considered "hot" in a specific location (table 1 and table 2 and table 3). (See 'Heat' above.)

•Risk factors for heat related illness – Several medical conditions, older age, certain medications, and biologic and social determinants are associated with greater heat-related morbidity and mortality. (See 'Risk factors for heat related illness' above.)

•Managing heat risk – Heat risk can be mitigated by using heat alerts, limiting exposure, using colling options, and developing heat plans. Disease-specific considerations are essential. (See 'Managing heat risk' above and 'Disease-specific considerations' above.)

●Wildfires – Living through a wildfire has both immediate and protracted physical and mental health effects. (See 'Wildfire health impact' above.)

•Wildfire smoke – Wildfire smoke creates widespread hazardous air quality conditions. Appropriate use of masks and actions to improve indoor air quality, including reduction of indoor air pollution sources and air filtration, may reduce harmful exposures. Certain patient populations are at increased risk of smoke related illness. (See 'Populations at increased risk' above.)

•Managing wildfire smoke risk – Identification of fire risk and hazardous air quality is necessary to identify when additional steps need to be taken. Fire-related air quality conditions for United States locations can be found at AirNow's Fire and Smoke Map, and forecasts for future air quality conditions can also be found at AirNow. The use of masks and improvement of indoor air quality are steps that can be taken to mitigate risk. (See 'Managing wildfire risk' above.)

●Hurricanes and floods – Hurricanes and floods have immediate and prolonged health risks. Immediate risks include unintentional injuries such as drowning, electrocution, lacerations, falls, head injuries from falling debris, motor vehicle accident trauma, and exposure to toxins. (See 'Hurricane and flood risks to health' above.)

•Managing risk – Preparing for floods and hurricanes centers on assessment of risk from forecasts and preparedness measures. Patients with significant chronic medical concerns, limited access to transportation, and smaller social networks, among other factors may be more vulnerable to harm. (See 'Managing hurricane and flood risk' above.)

●Power outages – Power outages can occur during climate emergencies and create risks for many patients with medical conditions. Care plans can incorporate guidance on how to reduce risks that may result from electronic medical equipment failure or reduced access to care. (See 'Power outage planning' above.)