Nonexertional

Nonexertional heatstroke---common in warmer, humid weather---results from environmental factors that raise body temperature. You might be taking part in mild to moderate activity but this is not the trigger.

Exertional

Exertional heatstroke occurs during strenuous physical activity in high temperatures, which raises your body temperature to dangerous levels.

Contributors

Wearing clothing that does not permit easy evaporation of sweat, consuming alcohol and dehydration can cause either kind of heatstroke.

Precursors

Heat cramps can lead to heat exhaustion, which progresses to heatstroke if untreated. People who experience cramps, lightheadedness, nausea or dizziness and thirst from hot weather or exercise should take appropriate measures---drinking water, taking a cold shower and/or finding shade or going indoors.

Risk Factors

Nervous system health affects ability to deal with heat---a problem for very young children and those over 65, reports MayoClinic.com. Genetics and lack of experience in heat puts you at risk. Certain medications---such as those for blood pressure or psychiatric issues---can lead to dehydration and interfere with your body's heat response.

Source:

The Mayo Clinic: Heatstroke