Heat-related illness is the spectrum of harm the body suffers when it can no longer shed heat — from heat cramps and heat exhaustion (heavy sweating, weakness, nausea, dizziness) up to heat stroke, a true medical emergency in which core temperature reaches 104°F (40°C) or higher, the sweating mechanism fails, and confusion or collapse follows. Heat stroke can cause permanent disability or death within minutes without emergency treatment.
This is the reason a broken AC is treated as an emergency at all. Extreme heat is the leading weather-related cause of death in the United States — the CDC counted 1,714 heat-related deaths in 2022, the most in decades, and recent summers have run higher. Indoors, an un-cooled home can climb past safe temperatures within hours during a heat wave, and a common-sense fix like a fan actually raises body temperature once the air is above about 90°F.
Risk is not evenly spread. Adults over 65, infants and young children, people with heart disease or diabetes, and those on certain medications cool themselves far less efficiently — which is why a no-cooling call at a household with an elderly resident is genuinely time-sensitive. Know the dividing line: heat exhaustion is treated by cooling down, resting, and drinking water; confusion, slurred speech, fainting, or hot, dry skin means heat stroke — call 911 immediately, then worry about the equipment. Restoring cooling matters, but a life-safety symptom always comes first.