When it is warm and dry: how to ventilate
Hot, dry weather is the easiest heat to work with. Close and shade by day, then open wide when outdoor air is cooler, often after sunset. Dew point stays low.
Hot, dry weather is the easiest heat to work with. Nights often cool down, and sweat evaporates, so a fan on your skin actually helps. The job is still the same: keep sun out by day, then open when outdoor air is cooler.
Dry heat from inland Spain, central Europe in a heatwave, or a desert-edge city behaves like this. Dew point stays low even when the thermometer is high. That is why a wide opening at the evening crossover usually works, unlike sticky humid heat.
The dry-heat checklist
- Close and shade sun-facing windows during the hottest hours
- Open wide once outdoor air is cooler than indoor, often after sunset
- Use a fan on you, not as a substitute for cooler outdoor air
- A short night flush beats leaving everything open into a hot morning
Catch the crossover, then shut again
Compare indoor and outdoor temperature. Do not open because the clock says evening. Open when the shaded outdoor reading drops below the room.
Shade the glass while you wait. Sun through a closed pane is still the main daytime heat source, even in dry air.
When outdoor air is cooler, flush the home as far as safety allows, then close before the morning heat climbs back through east-facing glass.
What a fan can and cannot do
A fan on your skin speeds evaporation. That works well when dew point is low. In an empty room the same fan slightly warms the air. Point it at people, or use it at a window to move cooler outdoor air, not as a pretend air conditioner.
If a dry heatwave ends and the building stays hot, keep night ventilation going. Walls release heat slowly. See why the home stays hot afterwards.
This is not medical advice. If heat is making you unwell, follow your local health agency.
Ventilate uses indoor temperature, local weather, sun, and layout to rank each window through a dry spell.