Heat cramps typically develop after exercise or other strenuous physical activity rather than from just being at rest in the heat. They can occur with exercise even if the temperature is mild or even cool.
Heat cramps are the mildest form of heat-related illnesses, which also include heat exhaustion and heatstroke. Heat-related illnesses can be classified as mild or severe. Common symptoms of heat cramps include:
- Heavy sweating (during intense exercise or prolonged exposure to high heat)
- Muscle pain or spasms (especially in the legs)
- Flushed, moist skin
If a person ceases activity, heat cramps usually start to improve within 30 minutes to an hour, sometimes longer. They may also come and go intermittently.
In some cases, heat cramps lead to severe heat-related illnesses, such as heat exhaustion and heatstroke. Heat exhaustion occurs when there is a significant loss of fluid and electrolytes due to prolonged exposure to extreme heat.
If heat exhaustion is left untreated, it can result in heatstroke, which is a potentially fatal condition that occurs when your internal body temperature reaches over 104 degrees.