The oppressive temperatures of a heatwave can have far-reaching impacts, from risks to human health to destroying crops and increasing the risk of wildfires. In 2019 alone extreme heat is estimated to have caused the deaths of 356,000 people worldwide, according to one set of estimates, making it one of the most dangerous yet overlooked natural hazards. While there is still a great deal of uncertainty about toll that heatwaves take, there is little doubt that the number of people exposed to heatwaves around the world is increasing.
And climate change is only likely to make heatwaves more frequent and intense in the future. Over the years, BBC Future has covered many different aspects of living with and enduring extreme hot weather. Here we round up some of what we have learned.
It’s crucial to stay cool in hot weather as it can have serious effects on your health (see further down this page). Fortunately, there are some simple steps you can take to find relief when the temperatures climb to uncomfortable levels.
Keeping out of the sun between 11am to 3pm – usually the hottest parts of the day – either by staying indoors or in a shaded area, is an obvious step. It is also important to drink plenty of liquid, including hot and cold drinks (unless it is very humid, in which case hot drinks aren’t the best idea). But it’s best to avoid drinking lots of alcohol, although a beer or two may still help to hydrate you.
Eating foods with high water content such as strawberries, cucumber, lettuce and watermelon can also help you to stay hydrated. Spicy and hot foods have also been shown to help us stay cool by making us sweat more.
While the evidence on the colour of clothing is mixed – there appears to be little difference between wearing light or dark clothing as a study of Bedouin tribes in the 1980s revealed – wearing loose-fitting clothes can help by allowing air to circulate next to your skin.
You should also think twice before you open all the windows of your house to keep cool – if the temperature if higher outside than inside, you might lose a possible cool haven. Close the curtains in rooms where they face the sun instead.
One of the easiest ways to stay cool can be to take advantage of the temperature change in the air when water evaporates. Taking a cold shower or a swim can help you cool down quickly. Ancient societies placed earthenware jars of water or wet sheets in front of a window or a draughty spot, helping to cool the air as it passes over it. This can also work if you are using a fan by blowing the air over a bowl of ice or cool wet sheet.
However, the evidence on the effectiveness of fans is quite mixed, largely due to a lack of good quality randomised trials. Generally, fans are thought to help in temperatures up to 35C (95F), but above that blowing hot air across the body could make the situation worse and even increase dehydration.