This is general information, not medical advice. Heat can be dangerous, and individual risk varies with age, health conditions and medications. Ask a doctor or other qualified professional about how to stay safe in hot weather if you have a medical condition or take regular medication, and follow local health and weather authority guidance during heat waves.
Why heat is a real health issue
The body works to keep its core temperature within a narrow range. In hot weather it mainly cools itself by sweating, and sweat only helps when it can evaporate. High humidity makes evaporation harder, so a humid day can feel more dangerous than the temperature suggests. As you sweat you lose water and salts, and if you do not replace fluids, you can become dehydrated, which makes it harder to cope with heat.
Most people get through hot days without trouble when they take simple precautions. But heat can cause illness ranging from mild cramps and fatigue to serious conditions that need emergency care, so it deserves respect.
Who may be at higher risk
Some people are more affected by heat, and should take extra care and check on each other:
- Older adults, whose sense of thirst and ability to adjust to heat may be reduced.
- Infants and young children, who depend on others to dress them and give them fluids.
- People who are pregnant.
- People with heart, lung or kidney conditions, diabetes, or other long-term illnesses.
- People taking certain medications, including some for blood pressure or mental health, and some that affect fluid balance. Ask a pharmacist or doctor whether yours do.
- Outdoor workers and people doing hard physical activity.
- People without access to cooling or air conditioning, or who live alone.
- Anyone not yet used to the heat, such as someone who has recently traveled to a hotter climate.
Never leave a child, person or pet in a parked car, even briefly. Temperatures inside a car can rise quickly and become dangerous.
Fluids
Drinking enough matters, and it is easiest to sip regularly through the day rather than wait until you feel very thirsty. Plain water is a good basic choice. Water-rich foods such as fruit, vegetables and soups also contribute, and there are plenty of hydrating foods beyond water. Very sugary drinks and a lot of alcohol are often not helpful in heat, and large amounts of caffeine can bother some people.
There is no single amount that suits everyone. Needs depend on body size, activity, climate and health, and some medical conditions require limits on fluids, so ask your doctor if you have been given guidance. Pale yellow urine is often used as a rough sign of reasonable hydration, but it is not a perfect test, and some vitamins or foods can change its color.
If you are sweating a lot over a long period, for example during sport or work, you may need more than water alone, such as food that contains salt. Check with a professional if you are unsure. Drinking extremely large amounts of plain water in a short time is also not recommended. For more on how fluid needs show up in everyday life, see the general advice on daily hydration, and for the effects of exercise, hydration during exercise.
Keeping your body and home cooler
- Dress for the weather. Loose, lightweight, light-colored clothing and a wide-brimmed hat are generally helpful outdoors.
- Use shade and plan the day. The hottest part of the day is typically midday to late afternoon. Schedule errands and exercise for early morning or evening where possible.
- Cool your surroundings. Close curtains or blinds on sunny windows, open windows at night if it is cooler outside, and use fans or air conditioning if available. Fans alone can be less effective in very high heat, so do not rely on them in extreme conditions. If you do not have cooling at home, spending a few hours in an air-conditioned public place such as a library or community center can help.
- Cool yourself directly. A lukewarm or cool shower, a damp cloth on the neck and wrists, and foot soaks can give relief. Very cold water is not required.
- Eat lighter. Many people feel better with smaller, lighter meals in the heat. Food safety also matters, since food left out spoils faster, so follow guidance on food storage safety.
- Protect your skin. Sunburn makes it harder for the body to cool itself. Use shade, clothing and sunscreen as part of everyday sun safety.
Exercise and hot weather
If you exercise outdoors, consider going shorter or easier, slowing down, taking breaks in the shade, and choosing cooler hours. Take water with you. It can take a week or two for the body to adjust to hotter conditions, so build up gradually. Strenuous exercise in extreme heat is not recommended without professional advice, and it is reasonable to skip or move indoors on the hottest days. Stop if you feel unwell.
Signs to take seriously
Heat illness can progress. Early signs may include heavy sweating, tiredness, thirst, headache, muscle cramps, dizziness and feeling faint or nauseated. If these appear, move to a cooler place, rest, loosen or remove excess clothing, sip water, and cool the skin with damp cloths or a fan.
Some signs suggest a medical emergency, and local emergency services should be contacted immediately:
- A very high body temperature, hot skin that may be dry or damp
- Confusion, slurred speech, strange behavior, or unusual drowsiness
- Fainting or loss of consciousness
- Seizures
- Vomiting that does not stop, or a rapid pulse or breathing
While waiting for help, move the person to a cooler place and try to cool them with water, damp cloths or fanning, and do not give fluids to someone who is not fully alert. Do not wait to see if symptoms pass if you see these signs, especially in an older person or a child.
Symptoms of dehydration can overlap with heat illness. Dark urine, a dry mouth, extreme thirst, little urination, dizziness and tiredness are some signs of dehydration worth responding to early.
Look out for others
Checking on neighbors, relatives and friends who live alone or have health problems can matter a lot in a heat wave. Agree on a time to check in. Help children and older relatives drink and cool down, since they may not do it on their own.
A short checklist
- Check the forecast and any heat warnings.
- Keep water within reach and sip regularly.
- Wear light clothing and use shade.
- Plan activity for cooler hours and go easier than usual.
- Know who is at higher risk and look out for them.
- Know the warning signs and what to do.
No set of precautions removes all risk, and responses to heat differ between people. When in doubt, err on the side of caution and ask a healthcare professional.