Heatstroke is a more serious disorder which may occur during Expeditions in hot conditions, particularly to unfit participants, when the body becomes dangerously overheated.  It can develop from heat exhaustion but is different from it.  The victim feels dizzy, giddy or faint with a rapid pulse rate, often followed by a headache, vomiting, muscle cramp, fainting and collapse to unconsciousness within minutes. 

Treatment involves resting the patient in a head-down position in the shade, natural or improvised, and cooling the head.  Cold water should be poured slowly over the clothing on the upper part of the body using a water bottle or cooking utensils.  The clothing will help to retain the moisture and promote evaporation, making a more effective use of the water if it is in short supply.  A folded wet towel should be placed on the forehead.  The patient should be fanned with a map case or towel.  If water is readily available, sponging the skin with an improvised sponge will be very effective.  Alternatively, immersion in a nearby water will relieve the condition.  Sipping plenty of cold water or other drink, to which a pinch of salt has been added, will replace body fluid and speed recovery.  The treatment must be continued until the situation has been completely stabilised.

If, like hypothermia, the symptoms are recognised in the early stages and prompt and effective action is taken, recovery is usually rapid.  However, heatstroke is a dangerous condition and medical assistance should be sought as soon as possible.  If the patient becomes unconscious, breathing and pulse should be carefully monitored and resuscitation administered if necessary.

Keeping the head and body well covered, frequent drinks, well-salted food and a rearranged schedule to enable travelling to take place in the early morning or the cool of the evening, instead of during the heat of the day, is a simple recipe for successful Expeditions in hot weather.