Weather Safety: The Complete Guide

How extreme heat, cold, wildfire smoke, storms, floods and power outages affect your health, who is most at risk, and the practical steps that keep your household safe before, during and after severe weather. It is for anyone in the US, and especially for people caring for children, older adults or someone with a chronic illness.

Key numbers at a glance

Why weather is a health issue

We tend to think of severe weather as a property problem: damaged roofs, flooded basements, fallen trees. But heat waves, cold snaps, wildfire smoke, hurricanes, floods and thunderstorms also cause illness, injury and death, and many of those harms are preventable. Extreme heat is a leading weather-related cause of death in the US. Carbon monoxide poisoning rises after storms. Wildfire smoke can make air unhealthy hundreds of miles from the fire. Floods kill people mostly in vehicles driven into moving water.

Weather also harms health indirectly. Power outages switch off air conditioning, heating, refrigerators and medical equipment such as oxygen concentrators. Storms can close pharmacies and clinics, cut off clean water and make roads impassable just when someone needs care. People who rely on daily medicines, dialysis or home oxygen can be in danger within days if they have not planned ahead.

The good news is that a handful of habits make a large difference: checking forecasts and alerts, knowing the warning signs of heat and cold illness, keeping a basic emergency kit, never running fuel-burning equipment indoors, and checking on people who are more vulnerable. This guide explains the reasons behind each step, so you can adapt them to where you live and who you live with.

Who is most at risk

Severe weather affects everyone, but not equally. Adults 65 and older are at higher risk in both heat and cold, because aging changes how the body controls temperature: older adults do not adjust as well to sudden changes in temperature and can lose body heat quickly, even indoors. Chronic illnesses such as heart disease, lung disease, diabetes and kidney disease add to the risk, as do medicines that affect sweating, fluid balance or alertness. Living alone is a risk in itself, because no one may notice when someone is getting sick.

Babies and young children are also more vulnerable. They heat up and cool down faster than adults, depend on others to dress them, give them fluids and move them out of danger, and cannot always tell you how they feel. Pregnant people are more affected by heat and by wildfire smoke. Outdoor workers, athletes, people experiencing homelessness and people who cannot afford to run air conditioning or heating face more exposure. Alcohol and some drugs make it harder to notice danger and to respond to it.

• Adults 65 and older, especially those living alone
• Babies and young children
• Pregnant people
• People with heart, lung or kidney disease, diabetes or mental health conditions
• People who take medicines that affect sweating, fluids or alertness
• Outdoor workers, athletes and people without stable housing
• People who rely on power-dependent medical equipment

Extreme heat: heat exhaustion and heat stroke

Your body cools itself mainly by sweating. When it is very hot, especially when it is also humid, sweat does not evaporate well, and your core temperature can climb. Heat illness ranges from heat cramps and heat rash to heat exhaustion, which is a warning sign, and heat stroke, which is a medical emergency. Heat exhaustion can turn into heat stroke quickly, so it is worth knowing the differences.

Signs of heat exhaustion include heavy sweating; cold, pale and clammy skin; a fast, weak pulse; nausea or vomiting; muscle cramps; tiredness or weakness; dizziness; headache; and fainting. If you notice them, move to a cool place, loosen clothing, put cool, wet cloths on the body or take a cool bath, and sip water. Get medical help if the person is vomiting, or if symptoms get worse or last longer than 1 hour.

Heat stroke happens when the body can no longer control its temperature. Signs include a body temperature of 103°F (39.4°C) or higher; hot, red skin that may be dry or damp; a fast, strong pulse; headache, dizziness, nausea, confusion; and losing consciousness. Call 911 right away. While you wait, move the person somewhere cooler and lower their temperature with cool, wet cloths or a cool bath. Do not give a person with heat stroke anything to drink.

Staying cool during a heat wave

The most protective step is time in air conditioning, especially during the hottest part of the day. If you do not have it at home, spend a few hours at a public cooling center, library or other air-conditioned building; your local health department can tell you where cooling centers are. When temperatures are in the high 90s °F, fans alone will not prevent heat illness. Drink more water than usual without waiting until you are thirsty, and limit sugary drinks and alcohol. Wear loose, lightweight, light-colored clothing, schedule outdoor activity for early morning or evening, and take frequent breaks in the shade. The CDC HeatRisk forecast can help you see which days carry the most danger where you live.

Hot cars

Never leave anyone, including children and pets, in a parked car, even with the windows cracked or for a few minutes. The temperature inside a car can rise to dangerous levels very quickly, even on a mild day, and young children heat up faster than adults. Make a habit of checking the back seat every time you leave the car, and keep cars locked so children cannot climb in on their own. If you see a child alone in a hot car, call 911.

Heat, medicines and chronic conditions

Several common medicines change how your body handles heat. Diuretics (water pills) and some blood pressure medicines increase fluid loss or lower blood pressure further when you are dehydrated. Some antidepressants, antipsychotics, anticholinergic medicines and stimulants can reduce sweating, raise body temperature or dull thirst and alertness. That does not mean you should stop them. Stopping or changing a medicine on your own because of the heat can be dangerous. Instead, before summer or a forecast heat wave, ask your doctor or pharmacist whether any of your medicines raise your heat risk and what to do about it.

If you have a condition that requires you to limit fluids, such as heart failure or kidney disease, ask your doctor how much to drink on very hot days rather than guessing. People with diabetes may find that heat affects blood sugar and that insulin and testing supplies are damaged by high temperatures. If you use insulin or other heat-sensitive supplies, plan how you will keep them cool during a power outage, and ask your pharmacist how long they stay usable once they get warm. Keep glucose tablets or another fast source of sugar with you on hot days.

Heat can also damage the medicines themselves. Most medicines should be stored at room temperature, away from heat and direct sunlight. Insulin, some inhalers and glucose test strips are particularly sensitive. Keep medicines out of hot cars, glove compartments and sunny windowsills, and if a medicine has changed color, texture or smell after heat exposure, ask a pharmacist before using it.

Extreme cold: hypothermia and frostbite

Hypothermia is a dangerously low body temperature, below 95°F (35°C), caused by losing heat faster than the body can make it. It is not just a risk on mountains or in blizzards. It can happen at temperatures above 40°F (4°C) if a person is chilled by rain, sweat or cold water, and it can happen indoors, especially to older adults in cold homes. Because hypothermia affects the brain, people often do not realize it is happening to them.

Warning signs in adults include shivering, exhaustion or feeling very tired, confusion, fumbling hands, memory loss, slurred speech and drowsiness. In babies, look for bright red, cold skin and very low energy. If you suspect hypothermia, take the person's temperature if you can. Call 911 if it is below 95°F or the person is confused, very drowsy or unresponsive. While waiting, move them somewhere warm, remove wet clothing, and warm the center of the body first (chest, neck, head and groin) with dry layers, blankets or skin-to-skin contact. Give warm, non-alcoholic drinks only if the person is fully alert. If they have no pulse, start CPR.

Frostbite is injury from freezing of the skin and the tissue underneath, most often on the fingers, toes, nose, ears, cheeks and chin. The first signs are redness or pain. As it worsens, the skin may turn white or grayish-yellow, feel unusually firm or waxy, or become numb. Because numb skin cannot feel heat, it is easy to burn during rewarming. Frostbite often occurs alongside hypothermia, which should be treated first.

• For frostbite, get into a warm place as soon as possible
• Put the affected area in warm, not hot, water, or warm it with body heat, such as fingers in an armpit
• Do not rub or massage the area, or use a heating pad, heat lamp, fireplace or radiator on numb skin
• Avoid walking on frostbitten feet or toes unless absolutely necessary
• Get medical care for skin that stays numb, white or grayish-yellow, or that blisters after rewarming

Staying warm and safe in winter

Dress in layers of loose, warm clothing, with a hat, scarf, mittens and water-resistant boots, and change out of wet clothes as soon as possible. Drinking alcohol to "warm up" is a myth: alcohol makes you feel warmer while your body actually loses heat faster. Indoors, older adults should set the thermostat to at least 68°F (20°C). If heating costs are a worry, the Low Income Home Energy Assistance Program (LIHEAP) can help with energy bills. Shoveling heavy snow is hard work that strains the heart, so if you have heart disease or are older and inactive, ask your doctor before doing it, take frequent breaks, and stop right away for chest pain or unusual shortness of breath.

Wildfire smoke and air quality

Wildfire smoke contains fine particles known as PM2.5, small enough to travel deep into the lungs and even into the bloodstream. Smoke can travel hundreds of miles, so air can be unhealthy far from any fire. Short-term effects include coughing, scratchy throat, irritated eyes, headaches and trouble breathing. Smoke can also trigger asthma attacks, worsen COPD and contribute to heart attacks and strokes in people with heart disease. Children, older adults, pregnant people and people with heart or lung disease are hit hardest.

The Air Quality Index (AQI) is the best everyday guide to how clean or polluted the air is. Check it daily at AirNow.gov or in the AirNow app when smoke is in your area. Higher numbers mean more pollution. From 101 to 150 the air is unhealthy for sensitive groups, from 151 to 200 it is unhealthy and anyone may start to feel effects, and higher levels are very unhealthy or hazardous. Use the AQI to decide when to move activities indoors, reduce exertion or close up your home.

Indoors, keep windows and doors closed and set air conditioning to recirculate. A portable air cleaner with a HEPA filter can lower indoor smoke levels; a do-it-yourself box fan filter can help too. Make one room a clean room where you spend most of your time. Avoid adding indoor pollution on smoky days by frying food, burning candles, smoking or vacuuming. If you need to be outside, a well-fitted N95 respirator can reduce exposure, while cloth masks, surgical masks, dust masks and bandanas offer little protection from smoke.

• AQI 0 to 50: good
• AQI 51 to 100: moderate; unusually sensitive people should consider reducing heavy exertion outdoors
• AQI 101 to 150: unhealthy for sensitive groups
• AQI 151 to 200: unhealthy for everyone; anyone may start to feel effects
• Above 200: very unhealthy or hazardous; everyone should limit outdoor activity

Hurricanes, emergency kits and planning ahead

Hurricanes, winter storms and other disasters can cut power, water and access to medical care for days. Planning before a storm is much easier than scrambling at the last minute, when stores are crowded and roads may be closing. Start with a household plan: know your local evacuation zone and route, agree on a family meeting place and an out-of-area contact everyone can call, and decide how you will care for pets. Follow evacuation orders from local officials; waiting too long can leave you trapped.

Keep two kinds of supplies: a go-bag you can grab if you need to leave quickly, and a larger kit for sheltering at home. Store at least 1 gallon of water per person per day for several days, and nonperishable food for several days with a manual can opener. Keep at least a 7-day supply of medicines, plus copies of prescriptions, a list of medicines and doses, and key medical information. Add a flashlight, a battery-powered or hand-crank radio, extra batteries, a first aid kit and phone chargers. Store copies of insurance cards and important documents in a waterproof bag.

Think about the people in your home with special needs. Babies need formula, diapers and supplies; older adults may need hearing aids, glasses, mobility aids and continence supplies. If anyone relies on medical equipment that needs power, such as oxygen, a ventilator or home dialysis, talk with the equipment supplier and your doctor about backup power and where to go if the outage lasts. Many utilities keep a list of customers with medical needs, so ask yours.

• Water: at least 1 gallon per person per day for several days
• Food: several days of nonperishable food and a manual can opener
• Medicines: at least a 7-day supply, with copies of prescriptions
• Light and information: flashlight, battery-powered or hand-crank radio, extra batteries
• First aid kit, phone chargers and copies of documents in a waterproof bag
• Supplies for babies, older adults and pets

Power outages and carbon monoxide

Carbon monoxide (CO) is an odorless, colorless gas released when fuel is burned in generators, grills, camp stoves, gas appliances, cars and fuel-burning heaters. Poisoning rises after storms and power outages, when people use generators and other equipment to stay warm or cook. CO builds up quickly in enclosed spaces, and people who are asleep or have been drinking can die before they have symptoms. When symptoms do appear, they include headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. Several people in a home feeling unwell at the same time, especially when they feel better outside, is a red flag.

The most important rule is simple: never use a generator, charcoal grill or camp stove inside a home, garage, basement, crawlspace or tent, even with the doors or windows open. Run generators outdoors only, at least 20 feet from windows, doors and vents. Never run a car in a garage, even with the door open, and never heat your home with a gas oven or stove.

CO alarms are your early warning system. Install battery-operated alarms, or plug-in alarms with battery backup, on every level of your home and near sleeping areas. Test them and replace batteries when you change your clocks in spring and fall. Have heating systems, water heaters and other fuel-burning appliances checked every year. If the CO alarm sounds, or you suspect CO poisoning, get everyone out to fresh air immediately and call 911.

Food and water safety when the power goes out

Keep refrigerator and freezer doors closed as much as possible. A closed refrigerator keeps food safe for about 4 hours; a full freezer holds its temperature for about 48 hours, and a half-full one for about 24 hours. Throw away perishable foods such as meat, fish, eggs, milk and leftovers that have been above 40°F (4°C) for 2 hours or more. Never taste food to check whether it is safe. If officials issue a boil-water advisory, follow its instructions exactly: boil water before drinking it or using it to cook, brush teeth or make baby formula, or use bottled water until officials say tap water is safe.

Floods, thunderstorms and lightning

Many flood deaths involve vehicles driven into flood water. Even shallow moving water can knock you off your feet or sweep a car away, and it is impossible to tell how deep water is or whether the road beneath has washed out. The rule is "turn around, don't drown": find another route rather than driving or walking through flooded roads. Water can also be electrified by downed power lines, so stay away from them and report them.

Flood water is not just water. It often carries sewage, chemicals and sharp debris. Do not let children play in it. During cleanup, wear rubber boots and gloves, wash with soap and clean water after contact, and keep cuts covered. Get medical care for any wound exposed to flood water, especially if it becomes red, swollen or oozing, and ask whether you need a tetanus shot. Throw away any food that may have touched flood water. Before entering a flooded building, make sure the power is off, and never run a generator or pressure washer indoors during cleanup. Dry out or remove wet materials as quickly as you can to limit mold growth.

Lightning can strike well away from the storm itself, and no place outdoors is safe when thunder can be heard. The rule of thumb is "when thunder roars, go indoors." Safe shelter means an enclosed building with plumbing and wiring, or a hard-topped metal vehicle with the windows closed. Open shelters, tents, picnic pavilions and spaces under trees are not safe. Stay inside until 30 minutes after the last thunder. Indoors, stay off corded phones and away from plumbing and electrical equipment, and get out of pools, lakes and the ocean.

Helping someone struck by lightning

People struck by lightning do not carry an electric charge and are safe to touch. Call 911 right away. If the person is not breathing or has no pulse, start CPR and use an AED if one is available. Many people survive lightning strikes, especially with fast help, which is one reason learning CPR is worthwhile for anyone who spends time outdoors with family, teams or groups.

Tornadoes

A tornado watch means conditions could produce tornadoes; a tornado warning means one has been seen or detected on radar and you should take shelter immediately. Go to a basement, storm cellar or a small interior room without windows on the lowest floor, such as a closet or bathroom, and protect your head and neck. Mobile homes and vehicles do not offer good protection, so know in advance where you would go. Keep sturdy shoes and a flashlight nearby during tornado season, since broken glass and debris cause many injuries afterward.

Outdoor workers, athletes and children

People who work or exercise outdoors face the most direct exposure to heat, cold and smoke. Workers who are new to hot conditions, or returning after time away, are at particular risk because the body takes time to adjust. NIOSH recommends that new workers spend no more than 20 percent of the usual time in the heat on the first day, increasing by no more than 20 percent each day after that. Water, rest and shade should be available, and workers should know the signs of heat illness in themselves and in each other. Employers have responsibilities under OSHA to protect workers from hazards including heat.

Athletes and coaches should plan practices for cooler times of day, build up gradually at the start of the season, allow frequent water breaks, and have a plan for cooling someone quickly if they show signs of heat stroke. On smoky days, move practices indoors or postpone them when the AQI is unhealthy. In cold weather, layers that can be removed as you warm up help prevent sweat from soaking clothing and chilling you later.

Children need adults to manage their exposure. Dress babies and young children in one more layer than an adult would wear in cold weather, and in light clothing in heat. Offer water often, limit outdoor play during the hottest part of the day and on unhealthy air quality days, and never leave a child in a car. Children with asthma should have an up-to-date action plan and their rescue inhaler on hand during smoke and heat events.

Older adults and neighbors who need checking on

Many deaths during heat waves and cold snaps are among older adults who live alone, often indoors and without working air conditioning or adequate heat. A daily phone call or visit can be life-saving. During heat waves, check on older relatives and neighbors at least twice a day, and look for signs such as confusion, unusual sleepiness, not drinking or not eating. Know where your local cooling and warming centers are, and help arrange transportation if needed.

Older adults should keep a list of their medicines and a supply of them ready for emergencies, plan ahead for any power-dependent medical equipment, and ask their doctor whether any medicines affect how they handle heat or cold. Relying on a fan alone in extreme heat, turning the heat down too low to save money in winter, and using a gas stove or oven to heat the home are all common and dangerous mistakes. LIHEAP can help with heating and cooling bills, and local agencies on aging can often help with fans, air conditioners or weatherizing a home.

A seasonal weather safety plan

Weather risks change through the year and differ across the country, from hurricane season on the Gulf and Atlantic coasts to wildfire smoke in the West and blizzards in the North. A short checklist for each season keeps preparation manageable. Adapt it to your region and to the people in your home, and sign up for local emergency alerts through your city or county so warnings reach your phone.

• Spring: test smoke and CO alarms when clocks change; review your household emergency plan and kit; learn where to shelter for tornadoes and thunderstorms
• Early summer: ask your doctor or pharmacist whether any of your medicines raise heat risk; service air conditioning; find your nearest cooling center; restock water and medicines before hurricane season
• Summer and fall: check HeatRisk and AirNow forecasts; buy N95 respirators and a HEPA air cleaner or box fan filter before smoke season; check on older neighbors during heat waves
• Fall: test CO alarms again; have furnaces, water heaters and fuel-burning appliances checked; prepare a winter car kit with blankets, water, snacks and a flashlight
• Winter: keep the thermostat at 68°F or above for older adults; dress in layers; never run generators or grills indoors; watch for signs of hypothermia and frostbite
• All year: keep at least a 7-day supply of medicines, copies of documents, and a plan for power-dependent medical equipment

Every guide in this topic

• Heat Exhaustion and Heat Stroke: What the Evidence Actually Says
• Heat and Medications: What Published Guidance Supports
• Hypothermia: What Published Guidance Supports
• Frostbite: What Published Guidance Supports
• Wildfire Smoke: What Published Guidance Supports
• Hurricane Preparedness and Emergency Kits: Sorting the Evidence From the Noise
• Carbon Monoxide During Power Outages: What the Evidence Actually Says
• The Evidence on Lightning Safety, Without the Hype
• What the Guidance Really Says About Flood Water Safety
• What the Guidance Really Says About Older Adults and Extreme Weather

Frequently asked questions

What is the difference between heat exhaustion and heat stroke?

Heat exhaustion is a warning sign: heavy sweating, cold and clammy skin, a fast weak pulse, nausea, cramps, dizziness or fainting. Cool down, loosen clothing and sip water. Heat stroke is an emergency: a temperature of 103°F or higher, hot red skin, a fast strong pulse, confusion or losing consciousness. Call 911 and cool the person while you wait.

Is a fan enough to stay safe in a heat wave?

Not in extreme heat. When temperatures are in the high 90s °F, fans alone will not prevent heat illness. Air conditioning is the most protective option. If you do not have it, spend the hottest hours in a cooling center, library or other air-conditioned place, take cool showers, and drink more water than usual.

Can my medicines make heat more dangerous?

Yes. Diuretics, some blood pressure medicines, some antidepressants, antipsychotics, anticholinergics and stimulants can affect sweating, fluid balance, thirst or alertness. Do not stop or change a medicine on your own. Ask your doctor or pharmacist before summer whether your medicines raise your heat risk, and keep medicines away from heat and direct sun.

How do I warm someone with hypothermia?

Call 911 if their temperature is below 95°F or they are confused, very drowsy or unresponsive. Move them somewhere warm, remove wet clothing, and warm the center of the body first: chest, neck, head and groin. Give warm, non-alcoholic drinks only if they are fully alert. If they have no pulse, start CPR while you wait for help.

What should I do if I think I have frostbite?

Get somewhere warm, and treat any signs of hypothermia first. Warm the area in warm, not hot, water or with body heat. Do not rub it or use a heating pad, heat lamp or fire, because numb skin burns easily. Get medical care if the skin stays numb, white or grayish-yellow, or blisters after rewarming.

Do masks protect against wildfire smoke?

A well-fitted N95 respirator can reduce how much smoke you breathe in. Cloth masks, surgical masks, dust masks and bandanas offer little protection. Masks are not a substitute for staying indoors with filtered air when the AQI is unhealthy, and people with heart or lung disease should ask their doctor before wearing a respirator.

Where should I put my generator?

Outdoors only, at least 20 feet from windows, doors and vents. Never run a generator inside a home, garage, basement, crawlspace or tent, even with doors or windows open. Install battery-operated CO alarms on every level of your home, and if an alarm sounds or anyone feels dizzy or sick, get outside to fresh air and call 911.

How much water and medicine should be in my emergency kit?

Store at least 1 gallon of water per person per day for several days, plus several days of nonperishable food and a manual can opener. Keep at least a 7-day supply of medicines, copies of prescriptions and a list of doses. Add a flashlight, radio, batteries, first aid kit, chargers, and supplies for babies, older adults and pets.

Is it safe to drive through a flooded road if the water looks shallow?

No. Even shallow moving water can knock you down or sweep a car away, and you cannot see whether the road underneath has washed out. Many flood deaths happen in vehicles. Turn around and find another route. If you are trapped by rising water, call 911 and move to higher ground if you safely can.

How long should I wait after a thunderstorm to go back outside?

Stay indoors until 30 minutes after the last thunder you hear. Lightning can strike well away from the storm, and many lightning injuries happen to people who went back outside too soon or were close to shelter. A building with plumbing and wiring, or a hard-topped metal vehicle with windows closed, is safe shelter.

When to speak to a doctor

Call 911 for signs of heat stroke (a temperature of 103°F or higher, hot red skin, confusion or passing out), hypothermia (a temperature below 95°F, confusion, severe drowsiness or unresponsiveness), anyone struck by lightning, anyone trapped by rising water, and chest pain or severe trouble breathing during smoke, heat or cold. If a CO alarm sounds or you suspect carbon monoxide poisoning, get everyone outside to fresh air and call 911; for questions about possible exposure, call Poison Control at 1-800-222-1222. Get medical care for heat exhaustion that involves vomiting or lasts longer than 1 hour, frostbitten skin that stays numb or discolored or blisters, and wounds exposed to flood water. Call your doctor before a heat wave or smoke event if you take medicines that affect fluids or temperature control, or if smoke worsens asthma, COPD or heart symptoms.

Where this comes from

• CDC — Heat-Related Illnesses
• CDC — Heat and Medications - Guidance for Clinicians
• CDC — Preventing Hypothermia
• CDC — Preventing Frostbite
• CDC — Carbon Monoxide Poisoning
• USDA — Keep Your Food Safe During Emergencies
• AirNow — Wildfire Smoke Guide for Public Health Officials
• American Red Cross — Make a Plan and Build a Kit
• National Institute on Aging — Cold Weather Safety for Older Adults
• NIOSH — Heat Stress

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.