I find it exactly the opposite. Then again, I originally spent a bit of my life in Phoenix AZ, so moving into the UK, I was more than surprised at the lack of sunshine and good weather.
Personally, I find that especially in the summer time, if you get up and get moving, even if its just a walk around the block, I sweat a lot less. I dunno why though. The heat makes you sweat more, and therefore, you have to push yourself harder.
If it gets too hot, I tend to workout inside my home, with a video workout, or wiifit, with my airconditioning unit focused on me.
