In the UK, cases of heat exhaustion and heatstroke usually only occur during periods of unusually hot weather, such as a heatwave. The risk may be greater when travelling abroad in hot countries.
At home
The government operates Heat-Health Watch, which is a system of four different warning levels based on the expected temperatures. This can be useful when planning activities or preparing for a heatwave.
The Department of Health's heatwave plan 2011 has advice on how to cope during a heatwave, including recommendations for preventing heat-related illnesses. The main recommendations are outlined below.
Stay out of the heat
Stay out of the sun during the hottest parts of the day, particularly between 11am and 3pm. However, it's important to remember that it can also be very hot before and after these times.
If you have to go out in the heat, make sure that you walk in the shade, apply sunscreen and wear a hat and light scarf.
Cool yourself down
Have plenty of cold drinks, but avoid drinks that contain caffeine and alcohol. Try and eat cold foods such as salad and fruit, which have a high water content.
Spraying water on your skin or placing a damp cloth on the back of your neck will help you cool down. You could also take a cool bath or shower.
Keep your environment cool
Place a thermometer in your main living room and bedroom to keep a check on the temperature. If possible, move into a cooler room, particularly for sleeping.
Keep windows that are exposed to the sun closed during the day. Open windows at night when the temperature has dropped. Consider replacing metal blinds or dark curtains as they absorb heat.
Have your loft and cavity walls insulated; this keeps the heat in when it's cold and keeps it out when it's hot. Use pale, reflective external paints.
Turn off non-essential lights and electrical equipment because they generate heat.
Grow trees and leafy plants near windows to act as natural air conditioners. Bowls of water in the house also cool the air through evaporation.
Look out for others
Keep an eye on isolated, elderly, ill or very young people. Make sure that they're able to keep cool. Ensure that they're not left alone in stationary cars during a heatwave.
Check on elderly or sick neighbours and elderly family members or friends every day if possible.
Be alert and call a doctor or social services if someone is unwell or further help is needed.
Travelling abroad
The advice above also applies if you're travelling abroad in a hot country.
It's important to remember that it takes the body 7 to 10 days to acclimatise to a hotter environment. Until that time, you will sweat less than you should. Drink water regularly, avoid staying in the heat too long and wear loose, light clothing.
Athletes should acclimatise for three to four days before undertaking anything but light physical activity, gradually building up activity levels over a two to three-week period.
Alcohol is also an important factor to consider when travelling abroad. Drinking too much alcohol can affect your ability to judge temperature and move to somewhere cooler. It can also contribute to dehydration, increasing the risk of heat exhaustion and heatstroke.
