Summertime fun. Let's be safe and stay hydrated.

Heat-induced symptoms, often precipitated by vigorous exercise, may include heat cramps, heat exhaustion, and heat stroke.
Heat cramps are painful involuntary muscle spasms that most often affect the calves, arms, abdominal muscles, and back. First aid for heat cramps includes rest, cooling off, and drinking an electrolyte-carbohydrate mixture, such as juice, milk, or a commercial electrolyte-carbohydrate drink. Stretching, icing, and massaging the painful muscles may be helpful. Exercise should not be resumed until all symptoms have resolved.
Heat exhaustion is caused by a combination of exercise-induced heat and fluid and electrolyte loss through sweat. Signs and symptoms may start suddenly and include:

• nausea
• dizziness
• muscle cramps
• feeling faint
• headache
• fatigue
• heavy sweating

Heat exhaustion is a serious condition because it can rapidly advance to heat stroke which can be fatal. Treat heat exhaustion vigorously by having the victim lie down in a cool place, take off as many clothes as possible, cooling with a cool water spray, and encouraging the victim to drink cool fluids, preferably containing carbohydrates and electrolytes.
Heat stroke and exertional hyperthermia are emergency condition characterized by a core temperature greater than 40°C (104°F) (severe hyperthermia) and central nervous system dysfunction (eg, confusion, seizures, coma). For these individuals, it is important to bring the body’s temperature down as quickly as possible to reduce the risk of organ injury or death. Immediately activate the EMS system and begin immediate cooling.
For adults and children with exertional hyperthermia or heat stroke, first aid providers should move the individual from the hot environment, remove excess clothing, limit exertion, and activate emergency services. (Class 1, LOE C-EO)(link opens in new window) {LINK: 2020 First Aid}(link opens in new window)
For adults with exertional hyperthermia or heatstroke, it is reasonable to initiate immediate active cooling by using whole-body (neck down) cool- to cold-water immersion techniques (1°C–26°C [33.8°F–78.8°F]), when safe, until a core body temperature of <39°C (102.2°F) is reached or neurological symptoms resolve. (Class 2a, LOE C-LD)(link opens in new window) {LINK: 2020 First Aid}(link opens in new window)
For adults with exertional hyperthermia or heatstroke, it may be reasonable to initiate other forms of active cooling, including commercial ice packs, cold showers, ice sheets and towels, cooling vests and jackets, evaporative, fanning, or a combination of techniques, when water immersion is not available. (Class 2b, LOE C-LD)(link opens in new window) {LINK: 2020 First Aid}(link opens in new window)
For children with exertional hyperthermia or heatstroke, it may be reasonable to initiate immediate active cooling by using whole-body (neck down) cool- to cold-water immersion techniques (1°C–26°C [33.8°F–78.8°F]), when safe, until a core body temperature of <39°C (102.2°F) is reached or neurological symptoms resolve. (Class 2b, LOE C-EO)(link opens in new window) {LINK: 2020 First Aid}(link opens in new window)
For children with exertional hyperthermia or heatstroke, it may be reasonable to initiate other forms of active cooling, including commercial ice packs, cold showers, ice sheets and towels, cooling vests and jackets, evaporative cooling, fanning, or a combination, when water immersion is not available. (Class 2b, LOE C-EO)(link opens in new window) {LINK: 2020 First Aid} 

https://cpr.heart.org/en/resuscitation-science/first-aid-guidelines/first-aid