I know that for me, working out in the summer isn't too bad. I got to spend some time in the Kalahari desert in southern Africa, and I would go jogging in the full sunlight. I also grew up outside Modesto.

I think a lot of it comes down to the mindset of working out - you have to decide "Ok, I am going to get disgustingly sweaty and be extremely hot. I am okay with that. In fact, I embrace the heat. Hotter is better."

Otherwise, you just hate it.

You must of course take the right precautions - lots of sunblock, lots of water before and after, a little Gatorade. I think the trick is to just embrace it.

Side note - worse than the heat, for me, is trying to run here when there is tons of crap in the area. Mid summer it's a lot more dust than it is pollen, but it's still pretty hard on the lungs.