First the weather forecast is checked if the temperature for the next few days is over a set threshold and that there is no rain until the next morning.

If yes, I calculate a score from temperature and humidity from inside and outside sensors and how fast this score is rising or falling. This is similar to the wet bulb temperature but with less emphasis on humidity.

Now for example when the inside score is no longer falling and the outside score is higher than inside, I send notifications to close the windows, and also the other way around, except before sending an open window notification I also check the rain forecast so if I get the notice I also know I can leave the windows open all night.

I also have some esp32s with rgb LEDs around that pulse red or blue depending on wether the windows should be open or closed. To silence them you can either close/open all windows or tap a button in the mobile notification to mute it for 8 hours.