My Delawares, who are from breeder stock, not hatchery, seem pretty heat tolerant- but upper 80's and 90 isn't anything like 100 degrees, so I can't say more than that. However, I can tell you they are super friendly, right from birth. They run TO you, not away from you, and like to hang out with you. I have several hens that will sit in my lap, and one young pullet that likes my shoulder better than any other place on earth. LOL! I have already posted pics here of my hens, and just got a new roo yesterday. I also hope to add more stock this fall or spring from another source. I am aiming for the standard.
BTW,even my skinniest hen lays pretty well - usually 6 out of 7 days a week, so I am impressed with that.