Lived only in southern states of America, I hate the heat and wish it never came back. I need to just move up north and stick to visiting via skype or something.
Worst experience was South Mississippi during Katrina, no power for a week, water pumps off and on. During extreme cold it could be horrible I'm sure, but at least you can layer til you can't move. When you're too hot you can't go beyond naked and that would just be miserable and torture.
When it's very hot like Summer currently you have to run to shelter or end up drenched spending any decent amount of time under direct sunlight. Ever play Mass Effect 2 where the sun scalds you, it feels like that but less deadly obviously.