Let me tell you. If you leave your car in the sun, after a few hours or less the temperature inside is more than 60 degrees C. It literally can melt a cheap plastic you left inside or destroy an electronic device you left inside (something with a crystall display etc).
So it is a absolute must here to open first you car let the "first heatwave" come out and then sit in the car and turn everything on. Can be dangerous if you just open the door start the engine and wait with the windows closed, the airconditioner to cool the car.
BUT after that as i said subaru aircon is top of the league compared with other cars (german for example)
Aircon is useful also in rainy conditions. It regulates the cabin moisture and prevents window or glass fogging (if i say it right). And that is tested. (and written in the manual)
The only reason i asked the UK "subaristas" is the language barrier with other countries.