Sunstroke is an overheating of the body as a result of prolonged exposure to the sun and direct effects of its rays. It can happen both while being in the sun and several hours later.

Sunstroke (heat stroke) can happen more quickly if you are dehydrated, wear thick or heavy clothing in hot weather, are overweight, are not used to heat, such as travelling from a cooler climate to a warmer one, take certain medications – antiallergic drugs, diuretics, laxatives, or antidepressants, when you are in a poorly ventilated or unconditioned space or suffered a heat stroke in the past.