It gets a bit toasty here from time to time....
Cornish x Rock cross seem to struggle in the summer, which I would attribute more to their fast growth genetics than their underlying breeds, since both Rocks and Cornish individually seem to do fine. I would say that the most problems come from birds with big fluffy feathers - orpingtons for example. Just sometimes seems hard for them to cool down, so, tighter feathering would be desired.. I would say that really dark or black birds tend to be at disadvantage unless there is a lot of shade handy. However barred rocks or rhode island reds tend to do fine. Large single combs seem to help somewhat - almost like a radiator or something. White or buff colors seem to do well also for obvious reasons, assuming you can keep away the hawks which spot those little bundles of white from a mile away. Really I haven't seen too many breeds that can't be managed, assuming good water and plenty of shade, as well as cover from predators. Losses from heat only are really quite low on any breed - even the Cornish cross or the Orpingtons. Mostly use common sense and I think most breeds of chicken will do fine in the heat.
What amazes me is how people can raise what are naturally tropical jungle fowl in the -20 degree weather of the northern states, Canada, and Alaska.
