Heatstroke is a condition caused by your body overheating, usually as a result of prolonged exposure to or physical exertion in high temperatures. This most serious form of heat injury, heatstroke can occur if your body temperature rises to 104 F (40 C) or higher. - mayoclinic.org

When undergoing a heat stroke,  the body overheats and can’t cool down by sweating because of dehydration. The risk of getting a heat stroke increases during hot and humid weather, especially if you are engaged in physical activity, are dehydrated, or have been directly exposed to the sun for too long.

Watch out for the following signs of heat exhaustion: intense thirst, dehydration, weakness or discomfort, dizziness or fainting, anxiety, and headaches.

You are suffering from a heat stroke if your core body temperature is 40°C or more; your skin is hot and dry; your heartbeat is rapid; or if you are suffering from convulsions, deliriums, and loss of consciousness, or even a coma.

To prevent a heat stroke limit the amount of time you spend outdoors, drink plenty of water; avoid tea, coffee, soda, and alcohol; wear a wide-brimmed hat and long-sleeved clothing outdoors; and schedule strenuous activities for the beginning or end of the day when it’s cooler.

To assist persons suffering from a heat stroke, move them to a shady spot or indoors and have them lie down with the legs elevated. If still conscious, have them sip cool water. Remove clothing, apply cool water to the skin and fan them. Apply ice packs to the armpits, wrists, ankles, and groin. Bring them to a hospital as soon as possible. - source: www.gov.ph