One is manageable. The other is a medical emergency.
Heat exhaustion means the body is overheating but still fighting. Symptoms include heavy sweating, cold and clammy skin, nausea, dizziness, headache, weakness, and a fast but weak pulse. The person is still sweating. That is the key differentiator.
Heat stroke means the body's cooling system has failed. CDC identifies the signs: body temperature above 103 degrees, hot and dry skin with no sweating, confusion or altered mental status, rapid and strong pulse, and possible loss of consciousness. The absence of sweating combined with hot, dry skin and confusion is the signal that the situation has crossed from manageable to life-threatening.
Heat exhaustion is treated by moving the person to a cool place, loosening clothing, applying cool wet cloths, and sipping water slowly. Heat stroke requires calling 911 immediately, then starting active cooling while waiting: move the person to the coolest location available, apply cold wet cloths or ice packs to the neck, armpits, and groin, and fan the skin. Do not give fluids if the person is confused or unconscious.
Elderly adults, young children, people with chronic conditions, and people taking certain medications (diuretics, beta-blockers, anticholinergics) are at higher risk. During multi-day heat waves, risk accumulates. The most dangerous period is often the second or third night, when indoor temperatures in homes without air conditioning never cool below the body's recovery threshold.
Manage heat gain, maximize airflow, know when to leave
CDC recommends a layered approach when AC is unavailable. During the day: close all windows, blinds, and curtains on sun-facing walls. Solar heat gain through windows is the largest contributor to indoor temperature rise. Dark curtains or reflective window film can reduce heat gain significantly.
After sundown, when outdoor air temperature drops below indoor temperature, open windows on opposite sides of the house to create cross-ventilation. Fans do not lower air temperature, but moving air across damp skin accelerates evaporative cooling. A wet towel draped over a fan, or a spray bottle used on skin in front of a fan, is more effective than a fan alone.
The most important room to cool is wherever people sleep. Sleep deprivation from heat compounds the physiological stress. Concentrate cooling efforts (fans, damp sheets, ice packs) in one room rather than trying to cool the whole house.
Know when the home is not enough. If indoor temperatures remain above 90 degrees at night and vulnerable people (elderly, infants, people with heart or lung conditions) are in the household, relocating to a cooled environment is the right call. Public cooling centers, libraries, malls, and friends' or relatives' homes with working AC are all better options than enduring dangerous indoor heat.
- Heat exhaustion: still sweating, clammy skin, nausea, weak pulse. Move to cool place, apply wet cloths, sip water.
- Heat stroke: stopped sweating, hot dry skin, confusion, strong pulse. Call 911. Cool aggressively while waiting.
- Ice packs at neck, armpits, and groin for active cooling.
- Day: close blinds and windows. Night: open for cross-ventilation.
- Fans + damp skin = effective evaporative cooling.
- If indoor temps stay above 90 at night with vulnerable people present, relocate.
- Heat Stroke Signs and Symptoms — CDC. Diagnostic criteria, emergency response procedure.
- Extreme Heat Prevention — CDC. Cooling strategies, high-risk populations, when to seek cooled shelter.
- Extreme Heat — Ready.gov / FEMA. Household planning, cooling center guidance.