[eldaisfish]

A more practical solution is to leave the windows slightly open so the hot air escapes.

[gabrielhidasy]

There are places where a marginally open window will invite vandalism, or rain, or bugs, or smoke and bad smells.

[eldaisfish]

ok, so in those places, you don't leave a window gap. in all the other places, you do.

[SoftTalker]

Not practical if rain is forecast.

[imp0cat]

The car already has a rain sensor so it can close the windows automatically. I do believe some VWs already do/did that.

[SoftTalker]

My car has that to activate the wipers. To say it works reliably is to lie.