The worst

yep, true facts, although some modern vehicles take only about 5 to 10 seconds to warm up enough, I highly recommend to wait at least half a minute or so to let it really warm up, especially in colder climates, in that case I recommend at least a few minutes like 2-5 at least.
REV UP YOUR ENGINES!

also a handy tip, if it's a hot day, and been driving, open the bonnet/hood when you get home or destination if you can. the heat by the engine can age the hoses quickly.

Same here in South Africa if you don't have aircon

Last I checked when the AC don't work in the heat, you use the backup a/c aka roll down the windows and hit the gas

Works if you are moving fast, but the wave of hot air alone if you aren't moving that fast or stuck in traffic doesn't make much difference.