OK, I will go against the flow here and say I am pooh sized, I live in Texas, and I wear jeans every chance I get -- even when it was 110 in the current heat wave. (Although I will admit that I don't go out that much when it's 110). I really don't understand the concept of "too hot for jeans".
Personally I find shorts much more uncomfortable in hot weather because of so much skin exposed to the sun. And because of problems of "chub rub" I generally don't like shorts or skirts. Some people here swear by skirts with bike shorts underneath, but I truthfully don't see how that's cooler than jeans.
Part of it probably depends on what you're used to. How hot does it get where you live? What do you wear there when it's really hot?