I ADORE hot weather, so my favorite is The Midnight Sun...until the twist ending, of course! I always go "ahhhhh" when the announcer on the radio says the weather is 110 degrees with 91% humidity :)
A close second is Twenty-Two. It looks like a home movie, which makes it look more real and all the more creepy. Room for one more, honey....scares the hell out of me every time!