I live in Magnolia, Texas... a little north of Tomball.
Hubby and I are going with a 100% Australorp flock. We want dual purpose birds that lay lots of eggs and give lots of meat that also do well in the brutal Texas heat.
Since Australorps were bred for heat tolerance in Australia, we figured it would be a very similar climate. I've also read that no matter which chicken you go with, you can make it work if you give them enough ventilation, water, shade and frozen fruit treats. :)
Good luck! We will learn together!
I am located about half way between Coleman, TX and Lawn, TX. We have the same brutal heat (high 90s to low triple digits) but not the level of humidity you have. I have 24 chickens. Columbian Wyandottes, Silver Laced Wyandottes, Barred and Partridge Rocks and Blue Andalusians. They have all dealt with the heat pretty well so far. To help I put gallon jugs of frozen water in their coop in the afternoons, usually 2 or 3. They cluster around the coolness. In addition I have a fan hanging outside the coop that blows in for circulation. I usually hang a frozen jug in front of it also and it does lower the inside temp by about 10 degrees. Lots of frozen treats like melon, peaches, strawberries and cold/chilled things like Romaine Lettuce. We also have to deal with the cold winters (19 degrees for three days last Feb) and, from what I have read, the chickens will deal with this pretty well without supplemental heat. I also have three Toulouse geese and 24 ducks which seem to do just fine in our heat.
Good luck with your Australorp flock. How many birds do you plan on. Watch out for chicken math by the way.