Heat is the leading weather-related killer in the US, responsible for approximately 700 deaths per year — more than tornadoes, hurricanes, and floods combined. The 2021 Pacific Northwest heat dome killed over 600 people in a region with low AC penetration. Unlike tornado or flood risk, heat risk is highly concentrated in specific populations and locations — understanding who is at risk and what cooling centers are available determines preparation priorities.
Heat Stroke vs. Heat Exhaustion: The Critical Distinction
| Condition | Core temperature | Skin | Mental status | Treatment |
|---|---|---|---|---|
| Heat exhaustion | Normal to elevated (<104°F) | Pale, moist, cool | Normal to dizzy/faint; no confusion | Move to cool environment; hydrate; rest; usually resolves |
| Heat stroke (classic) | ≥104°F (40°C) | Hot, dry (not sweating in classic form) | Confused, disoriented, may be unconscious | EMERGENCY: aggressive cooling + 911 immediately |
| Heat stroke (exertional) | ≥104°F (40°C) | Hot and often still sweating | Confused, aggressive behavior, loss of coordination | EMERGENCY: same as classic |
Classic heat stroke occurs in the elderly or those with compromised thermoregulation without exertion — commonly during multi-day heat waves with warm nights that prevent core temperature recovery. Exertional heat stroke occurs in young, healthy people during intense activity in heat. Both require immediate medical treatment — heat stroke is a medical emergency with a mortality rate above 50% without treatment.
Emergency Cooling for Heat Stroke
Call 911 first, then begin cooling immediately. Every minute at high temperature increases tissue damage:
- Cold water immersion: The fastest cooling method. Fill a tub with ice water or cold water; immerse the torso. Target core temperature below 102°F. If no tub: wrap the person in wet sheets with ice on the neck, armpits, and groin (where large blood vessels are close to the surface).
- Fan + misting: A fan blowing air over wetted skin is effective when cold water immersion is unavailable. Wet the skin, fan vigorously.
- Do not give fluids to a confused or unconscious person — aspiration risk. Wait for IV access at the hospital.
Vulnerable Population Risk Factors
- Age over 65: Reduced thermoregulatory capacity; reduced thirst sensation; often on medications that impair heat dissipation. Check on elderly neighbors twice daily during heat waves.
- Medications: Diuretics reduce body water; anticholinergics (antihistamines, Benadryl) impair sweating; beta blockers limit cardiovascular response; psychiatric medications impair hypothalamic regulation. If you take any of these, your heat tolerance is reduced.
- Lack of air conditioning: The single strongest predictor of heat stroke death. In the 1995 Chicago heat wave, 740 deaths — the majority were in homes without AC and with closed windows.
- Urban heat island: Urban areas can be 5–10°F hotter than surrounding suburbs due to asphalt, concrete, and reduced vegetation. Top-floor apartment residents in urban areas face significantly higher heat exposure than the reported ambient temperature suggests.
Wet Bulb Globe Temperature: A Better Risk Measure
Air temperature alone is a poor indicator of heat risk. Humidity determines how effective evaporative cooling (sweating) is. The wet bulb temperature combines air temperature and humidity into a single risk indicator:
- At wet bulb temperature of 90°F (32°C): heat stress for most people; even healthy adults are at risk during sustained exertion
- At wet bulb temperature of 95°F (35°C): the theoretical limit of human survivability — core temperature cannot be maintained through sweating alone even at rest in the shade
- Wet bulb temperature is available on weather.gov or in heat stress apps. It is reported as “wet bulb temperature” or approximated by the “heat index” (a related measure)
Cooling Without Air Conditioning
- Night-flush cooling: Open windows and run fans to bring in cooler night air; close up the house in the morning before heat builds. Effective if nights fall below 75°F.
- Evaporative cooling (swamp cooler): Effective in dry climates (below 30% humidity). Ineffective in humid conditions.
- Cold water immersion: Fill a bathtub with cold water; immerse yourself periodically. More effective than fans or evaporative cooling in high-humidity heat events.
- Cooling centers: Public air-conditioned spaces designated by local emergency management during heat emergencies — libraries, community centers, malls. Find your local cooling center through your city’s emergency management website.
Vehicle stranding in extreme heat — including heat stroke risk assessment and signaling for help — is in vehicle emergency preparedness: breakdown, stranding, tire blowout, and submersion.
