What does hot weather do to the body?

Image source, Getty Images By Jennifer Clarke Published 25 July 2019 Updated 22 June 2026 Periods of hot weather can affect anyone, but some people run a greater risk of serious harm. Experts recommend that those who may be more vulnerable - such as older people and babies and young children - should take extra precautions. What does extreme heat do to our bodies? As the body gets hotter, blood vessels open up. This lowers your blood pressure and makes your heart work harder to push the blood around the body. This process can cause mild symptoms such as an itchy heat rash or swollen feet. At the same time, sweating leads to the loss of fluids and salt and, crucially, the balance between them in the body changes. This, combined with the lowered blood pressure, can lead to heat exhaustion. Symptoms include: dizziness nausea fainting confusion muscle cramps headaches heavy sweating tiredness If blood pressure drops too far, the risk of heart attacks rises. How does sunscreen work, and how much do you need to use? Published 22 June Staying safe in water when the weather's hot Published 27 May Why do bodies react this way to heat? Our bodies strive to keep a core temperature of about 37C whether we are in a snowstorm or a heatwave. That is the temperature at which our bodies have evolved to work. But as the weather gets hotter, it is harder for the body to keep its core temperature down. It opens more blood vessels near the skin to lose heat to our surroundings and starts sweating. As the sweat evaporates, it dramatically increases the heat lost from the skin. How can I stay safe in the heat? Image source, Getty Images The UK Health Security Agency (UKHSA) recommends looking out for those who may struggle to keep cool, such as older people, those with underlying conditions and those who live alone. Other advice includes: staying cool indoors by closing curtains on rooms that face the sun drinking plenty of fluids and avoiding too much alcohol keeping out of the sun between 11:00 and 15:00 when the sun's rays are strongest staying in the shade, using sunscreen with a high SPF and UVA rating , and wearing a wide-brimmed hat avoiding physical exercise in the hottest part of the day carrying water with you if travelling Anyone tempted to cool off in rivers and open water should consult local warning signs and consider any hidden dangers , external . No one - especially babies, young children and animals - should ever be left in a locked vehicle. Hot weather: How to sleep in the heat Published 25 June Six ways to keep your home and yourself cool in hot weather Published 22 June When is it too hot to walk your dog? Published 22 June What should I do if I think someone has heat exhaustion or heatstroke? If you see someone you think has heat exhaustion , the NHS says you should: , external move them to a cool place get them to lie down and raise their feet slightly get them to drink plenty of water - sports or rehydration drinks are also OK cool their skin -