When is the best time to open my windows?

Best ventilation happens when the outdoor temperature is at least 2°C cooler than indoor and humidity is below 70%. In summer that's typically early morning (5–8 AM) or after sunset. In winter, short bursts (5–10 min) of cross-ventilation a few times per day.

Should I open the windows when it's hot outside?

No. If the outdoor temperature is higher than indoor, opening windows brings warmer air in and worsens comfort. Keep them closed and shaded during the hottest hours, then open at night when temperatures drop.

What humidity level is too high for ventilation?

Above 80% relative humidity outside (especially when warm), opening windows makes indoor air feel sticky and can promote mould. Wait for drier hours or use a dehumidifier.

How does OpenWindow.live decide?

We compare your outdoor real-time data (OpenWeather + AQICN) against your indoor reference temperature (configurable). Hard NOs: AQI very poor, outdoor warmer than indoor, humidity > 80% in warm weather. GREEN: outdoor cooler by 2°C+ with clean air. Otherwise yellow with a partial-ventilation tip.

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Should I open the windows in Washington D.C. right now?

Live decision for Washington D.C.. Updated every 30 minutes.

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When is it best to open windows in Washington D.C.?

In Washington D.C., the best ventilation times are typically early morning (5–8 AM) and late evening (after sunset) when outdoor temperatures drop below indoor levels.

Is it safe to leave windows open at night in Washington D.C.?

Yes, in most weather conditions. Open windows can drop indoor temperature by 2–5°C in 30 minutes if outdoor air is cooler. Check the live recommendation above for tonight.

What outdoor humidity is too high for ventilation?

Above 80% humidity, opening windows can make indoor air feel sticky. Combine with dehumidifier or wait for drier hours.

Should I open the windows in Washington D.C. right now?

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