If not regularly replaced, the loss of salt and water can slowly lead to heat exhaustion so sip water regularly and take on salts through food like bananas and nuts. Look out for muscle cramps, headaches, dizziness, upset stomach, nausea, clammy skin… all symptoms of heat exhaustion. If anyone shows these symptoms then get them to remove excess clothes and rest in a cool place with plenty of water to drink. They should feel better within half an hour.
Heatstroke is more serious and shows the body core has overheated to such an extent that it cannot cool itself. Dry skin, headaches, confusion, vertigo, nausea, thirst, hyperventilation, cramps… don’t hang around. Get the person into a cool place with plenty of water to drink. Cool the body with a fan, cool water (not cold) and/or wet towels. Seek medical aid.
TIP During the day eat small, cold meals that have high water content, like salads and fruit. Avoid caffeine and alcohol.