Desert hikes, summer portages and long climbs all carry heat risk. The CDC separates heat illnesses by severity. Telling heat exhaustion from heat stroke quickly decides whether you treat it on the trail or call for help immediately.
Heat exhaustion: treat it now
Signs include heavy sweating, cold, pale and clammy skin, a fast weak pulse, nausea or vomiting, muscle cramps, tiredness, dizziness, headache and fainting.
- Move to a cooler place and stop physical activity.
- Loosen clothing and apply cool, wet cloths.
- Sip water.
- Get medical help right away if vomiting, if symptoms worsen, or if they last over an hour.
Heat stroke: a medical emergency
Signs include a body temperature of 103°F or higher, hot, red, dry or damp skin, a fast strong pulse, headache, dizziness, nausea, confusion and losing consciousness.
Call 911 right away. Move the person somewhere cooler and lower their temperature with cool cloths or a cool bath. The CDC says not to give the person anything to drink.
Prevention on the trail
Carry extra water and sun protection; both are among the Ten Essentials. Plan strenuous stretches for cooler hours and know where shade and water are on your route.
Quick answers
What is the difference between heat exhaustion and heat stroke?
Heat exhaustion brings heavy sweating and cold, clammy skin; heat stroke brings 103°F or higher, hot red skin and confusion and needs 911.
Should you give water to someone with heat stroke?
No. The CDC says not to give a person with heat stroke anything to drink; call 911 and cool them.
General education, not medical advice or a substitute for training. In an emergency, call 911 or your local emergency number. Updated 2026-10-26.