The short answer
Smoke guidance often favors closed windows, while heat guidance may favor cooling or ventilation. Do not solve one exposure by ignoring the other. Use mechanical cooling and filtration when they work together. If the home cannot remain both cool enough and clean enough, move early to a cooled, filtered place. There is no universal instruction to keep windows closed at any indoor temperature, and no universal instruction to open them whenever the home feels hot. The decision depends on current indoor heat, outdoor smoke, equipment, household sensitivity, and a reachable alternative.
Start here
- Official instructions and symptoms. Evacuation, fire, severe illness, or emergency directions take priority.
- Indoor heat. Is the occupied room still warming? Is anyone showing heat-illness symptoms or unable to recover overnight?
- Indoor smoke control. Can windows stay closed while air conditioning and filtration reduce exposure?
- The fallback. If the home cannot manage both conditions, where can the household go before travel becomes difficult?
If the home has effective cooling
Close windows and doors while outdoor smoke is unhealthy, use recirculation where the equipment permits it, and run effective particle filtration in the occupied room. Shade sun-exposed windows, reduce indoor heat sources, and concentrate activity in the room the household can keep coolest and cleanest.
Check that the cooling system is not intentionally drawing outdoor air. A portable air cleaner does not cool the room; an air conditioner does not necessarily remove smoke particles. Use each for the job it can actually do.
If the home has no effective cooling
A closed home can continue heating after sunset. Fans move air but do not cool it, and CDC advises not relying on a fan at an indoor temperature of 90°F or above. Opening windows may lower heat exposure only when outdoor air is cooler and clean enough. During heavy smoke, that tradeoff may not be acceptable.
Do not wait for the home to become intolerable before identifying another place. Options may include a public cleaner-air or cooling location, a library or community building that officials identify as open, or a private destination confirmed by the household. Verify hours, access, transportation, animal rules, electricity for equipment, and whether the site is actually cooled and filtered.
Make the fallback usable
Make the destination usable before the household needs to leave:
- Identify more than one destination and confirm which can provide both cooling and filtration.
- Check opening hours, current availability, accessible entry, animal rules, and power for essential equipment.
- Record a route, a second route or destination, and how everyone will travel.
- Keep directions and essential phone numbers available on paper or saved for use without a connection.
- Agree who should hear from the household when it leaves and arrives.
Reconfirm before setting off when possible. Current official instructions, road conditions, the destination's real status, and the household's observations remain authoritative.
During the event
- Check current official smoke and heat information and note when each source was updated.
- Watch the occupied room, not only the outdoor forecast. If no thermometer is available, worsening symptoms, a room that keeps heating, and lack of nighttime relief are still meaningful.
- Keep medicines, mobility or medical equipment, animals, and transportation in the decision.
- Leave early enough to travel safely if the current setup is failing. Do not wait for a device battery, indoor temperature, or person's condition to reach its last possible limit.
- Call emergency services for severe symptoms, confusion, fainting, chest pain, marked breathing difficulty, or another possible emergency.
When outdoor air temporarily improves
If official information shows that outdoor air has become cleaner and the outdoor air is cooler, ventilating can remove accumulated indoor heat and pollutants. Recheck before opening, use safe windows, and close them again if smoke or outdoor heat worsens.
What not to do
- Do not keep a home closed against smoke while ignoring dangerous indoor heat.
- Do not open windows for heat without checking current smoke and other outdoor hazards.
- Do not assume a cooling center is filtered, a cleaner-air space is cooled, or either is open and accessible.
- Do not rely on a fan as the heat plan at 90°F indoors or above.
- Do not treat a cached route, old AQI value, or saved destination as current confirmation.
Next action
Compare the chosen cool room and cleaner-air room. If one place cannot do both jobs, record a cooled, filtered destination, a second option, directions available without a connection, and the people the household will contact.
What changes this answer
General guidance becomes a personal decision through these details.
smoke particles, temperature, overnight low, fire proximity, power, roads, and official instructions.
indoor temperature and trend, air leakage, cooling, filtration, window safety, and which room can manage both exposures.
heat and smoke sensitivity, symptoms, animals, equipment, medications, mobility, transport, and communication needs.
actual hours, cooling, filtration, capacity, accessibility, animal policy, power, route, and current availability.
Where this guidance stops
- Overshot cannot certify that a home, route, shelter, public facility, or private destination is safe or open. It cannot diagnose illness, detect indoor pollutants, or originate an evacuation threshold. Current official instructions and emergency services take priority.
Sources
Consequential guidance is checked against the linked source material.
- AirNow. Protect Yourself from Smoke and Extreme Heat. Checked September 24, 2026.
- U.S. Environmental Protection Agency. Create a Clean Room to Protect Indoor Air Quality During a Wildfire. Checked September 24, 2026.
- U.S. Environmental Protection Agency. Indoor Air Filtration. Checked September 24, 2026.
- Centers for Disease Control and Prevention. About Heat and Your Health. Checked September 24, 2026.
General information, not advice tailored to you or a guarantee of safety. You are responsible for decisions about your safety. Follow current directions from local authorities. Read the safety disclaimer.