Hi Graydog;
It's not so much the heat as it is the humidity.
The summers are really no hotter then they were in Denver, in the mid to high 90's, seldom 100 or higher (but it does happen some years). Dallas actually gets hotter then we do but they have less humidity as they are so far from the Gulf of Mexico.
The real problem is that we are so close to the Gulf of Mexico (about 30 miles north) that the summer winds almost always blow from the South bringing in a lot of humidity off of the Gulf.
A comparison between Denver & Houston summer humidity is...
Denver; Day... 10-25%, Night... 10-25%.
Houston; Day... 50-80%, Night... 80-100%.
Yes; it is very humid but virtually everything is air conditioned. Even Six Flags amusement park has outdoor areas that are air conditioned. This is a great city for air conditioner contractors & service companies.
We do however make up for it in the wintertime. It has snowed only three times since 1963 & only one of them amounted to anything (2 inches & lasted for a couple of days). The winters are very nice, cool (around 40-60 degrees F), low humidity (for us) as the wind often blows from the north bringing in dryer air. Our winters are a lot like Denver's spring & fall (cool & dry).
I love the winters here but still miss the snowfall, especially around Thanksgiving, Christmas time, and New Years.