Look at Privett's site and go into some of the breeds' descriptions. They have some blue plymouth tint, and some other blue plymouth types, that if you look at it right, sound like they must have some andalusian in them, which is a good extreme-heat tolerant breed. These descriptions say that "the males are....." which is your clue. They also have a red breasted blue leghorn (or blue breasted red) that is auto sexing, that's generally a fairly heat tolerant breed.
Other birds that are more heat tolerant than average, are the sapphire gem (hoover's hatchery) and the midnight majesty marans (also hoover's), but the latter has feathered feet. I believe crele penedesenca are auto sexing if you can find them. Cream legbars are auto sexing, not sure about heat tolerance. The possible legbar I have is OK though.