I lived in Houston for six years and really loved it.
Yes, I had to become accustomed to the heat because I am from New Jersey. The temperatures easily reached the upper 90's, at least, starting in late May and continued like that through the end of September. I would say we went over 100 at least 1/4 to 1/3 of the time.
You just learn to hydrate, pace yourself, avoid overexertion and too much exposure to the sun, etc. And while Houstonians aren't wimps by any means, they sure know how to crank the AC.
I began commuting to work by bicycle, 8.25 miles each way, in 1997 and continued this until 2002. I really enjoyed it. The mornings were not a problem, because it was still usually in the 70's and I was moving most of the time on the bicycle, so I would have a little sweat on my back at most. I'd towel off and get dressed in my office.
The ride home at 4 p.m. was another matter. Oh my. Walking outside into the heat was like walking into something almost solid. It literally took my breath away for a moment. But I would just get on my bike and go. The ride was about 45 minutes. I was quite sweaty at the end of the ride, but that's not such a problem when home is your destination. The only part of that trip home that really bothered me was being stopped at a red light behind traffic, because then I would just bake -- with the addition of hot car exhaust.
I miss Houston very, very much and I still have friends there. I plan to visit this Christmas.