Staying safe in extreme heat without air conditioning — passive cooling, window management, body cooling, recognising heat illness, and protecting vulnerable people.
The 2003 European heatwave killed an estimated 70,000 people — most of them elderly, most of them at home, most of them without air conditioning. The 2021 Pacific Northwest heat dome saw temperatures exceeding 49°C in regions that virtually no home had been built to tolerate, killing over 600 people in Canada and the US combined in just a few days. Heat is the deadliest weather phenomenon in most temperate countries, yet it receives far less attention in emergency preparedness than dramatic events like floods or fires. With climate change increasing the frequency and intensity of heat extremes, knowing how to keep a building and a body cool without air conditioning is a life skill of increasing urgency.
Heat kills through a cascade of physiological failures, not all at once:
Heat cramps: Painful muscle spasms, usually in legs or abdomen. Caused by electrolyte loss through sweating. Earliest warning sign of heat illness.
Heat exhaustion: Heavy sweating, cold and pale or clammy skin, fast and weak pulse, nausea, weakness, dizziness, possible fainting. The body is struggling to maintain temperature but has not yet failed.
Heat stroke: Body temperature above 40°C (104°F), hot and red skin (may be dry or damp), rapid and strong pulse, confusion, slurred speech, possible unconsciousness. This is a life-threatening emergency.
| Condition | Core Temp | Key Signs | Action |
|---|---|---|---|
| Heat cramps | Normal | Muscle cramps, sweating | Rest, cool area, electrolytes |
| Heat exhaustion | Up to 40°C | Cold pale skin, heavy sweating, weakness | Move to cool area, cool body, fluids |
| Heat stroke | Above 40°C | Hot skin, confusion, may stop sweating | Emergency — cool rapidly, call 000/999/911 |
⚠️ When someone stops sweating in the heat and becomes confused, this is heat stroke — a medical emergency. Call emergency services immediately while beginning rapid cooling. Every minute of delay increases organ damage and death risk.
The following groups face dramatically elevated risk:
Before focusing on body cooling, optimise the building itself. A well-managed building stays significantly cooler than the outdoor air during a heatwave.
Block solar gain — this is the single most important action:
Seal hot air out: 5. Close windows when outdoor air is hotter than indoor air (typically from mid-morning to evening). 6. Seal door gaps where hot air can flow from unconditioned areas (e.g., a hot garage, stairwell).
In most heatwaves, outdoor temperatures drop significantly after midnight — sometimes by 10°C or more. This is your window for passive cooling:
⚠️ Stop ventilating and close all windows by approximately 7–8 am, before outdoor temperatures rise above indoor temperatures. The thermal mass of the building then acts as a heat buffer through the day.
Different rooms heat at different rates:
Even when the building is not ideally cool, direct body cooling is highly effective.
This is not optional — it is physiological survival:
Cooling the blood where it flows close to the surface quickly reduces core temperature:
A damp cloth placed on the back of the neck can provide significant cooling relief. Refresh it as it warms.
A cool (not cold) shower reduces core temperature rapidly and provides sustained relief as evaporation continues from damp skin. Lukewarm is more effective than ice cold for sustained relief — cold water causes peripheral vasoconstriction, reducing the skin's ability to radiate heat.
No shower available: Fill a spray bottle with water and mist the skin; a small battery-powered fan directed at misted skin accelerates evaporative cooling dramatically.
Hang damp sheets in doorways — air flowing through a wet sheet is cooled by evaporation. This is the principle behind a swamp cooler (evaporative cooler), which is effective in dry climates.
⚠️ Evaporative cooling is less effective in high-humidity climates. When the air is already saturated with moisture, sweat does not evaporate efficiently and the body cannot cool by sweating. In high humidity (above 60–70%), prioritise shade, limiting activity, and hydration over evaporative techniques.
Avoid physical exertion during the hottest part of the day (10 am – 6 pm during severe heatwaves).
Poor sleep in heat is a significant compounding factor in heat illness, as the body does not cool as effectively during poor-quality sleep.
During heatwaves, elderly people living alone are at extreme risk. The 2003 European heatwave deaths were disproportionately elderly people who had not been checked on for days. Establish a checking system:
Review medications with a pharmacist or GP before a heatwave if you or a family member takes:
During severe heatwaves, local authorities typically open cooling centres — air-conditioned public spaces where residents can spend the hottest hours of the day:
| Situation | Action |
|---|---|
| Building management | Block sun in morning; close windows when outdoor temp > indoor temp; ventilate at night |
| Body cooling | Cool damp cloth on pulse points; mist skin + fan; cool (not cold) shower |
| Hydration | 3–4+ litres/day in heat; include electrolytes; avoid alcohol |
| Heat exhaustion (pale, sweaty, weak) | Cool room, cool body, fluid with electrolytes, rest |
| Heat stroke (confused, hot, may stop sweating) | Emergency — call 000/999/911, cool rapidly |
| Sleeping hot | Damp sheet, coolest room, frozen bottle, minimal bedding |
| Elderly living alone | Check twice daily; know signs of heat illness |
| High humidity | Evaporation less effective; prioritise shade and rest |
This article provides general guidance on managing extreme heat without air conditioning. Heat stroke is a medical emergency requiring immediate professional medical attention. If in doubt about someone's heat illness severity, call emergency services.
Take Staying Cool Without Air Conditioning with you — no internet needed when it matters most.
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