Hot weather can place strain on anyone, not only older people or those with long-term illness. Healthy adults who exercise outdoors, work physically demanding jobs or become dehydrated can also develop heat exhaustion or, in severe cases, heatstroke.
Why exercise becomes harder in the heat
The body sheds heat partly by increasing blood flow to the skin and by sweating. Strenuous exercise adds more internal heat, while sweating increases fluid loss. Hot, humid conditions make cooling less effective.
That is why NHS hot-weather guidance advises avoiding exercise or activity that makes you hotter during the hottest parts of the day. Moving a run to early morning or evening, shortening the session or skipping it entirely during extreme conditions can be a sensible adjustment rather than a loss of fitness.
Alcohol and hydration
Alcohol is not a useful hydration strategy in hot weather. NHS guidance recommends drinking extra fluids and avoiding alcohol when trying to keep cool and hydrated.
People do not need to panic about every warm day, but they should pay attention to symptoms such as dizziness, headache, nausea, unusual tiredness or confusion.
Keep the advice proportionate
Claims that a particular heatwave is causing a surge in cardiac arrests among young, fit people require specific epidemiological evidence. The general public-health message is simpler and better supported: extreme heat increases physiological stress, and vigorous activity can increase that burden.
Anyone who develops signs of severe heat illness, including confusion, collapse or a very high temperature, needs urgent medical help.
Source: NHS, “Heatwave: how to cope in hot weather”, reviewed June 2026.
