I had 3 bsl pullets and 3 roosters ( I know roosters lol ) in a 12x16 run with a 8'x10' coop with plenty of shade around it and under the coop which I have 3 sided wood so they always have shade, they were perfectly happy in there but I decided that since I have not let them free range yet then I will "expand their horizons" by putting 3 16' hog panels against their run to make an extension so they can get out and eat fresh grass and dig around. They have done great the last 2 weeks, when I go let them out of their coop in the morning I leave the run door open all day and they come and go as they please in the extended area. The temps today are around 102 and the heat index around 112, EXTREMELY HOT since yesterday was mid 80s and they last week has been 70's. Today I am down with pneumonia so I only got to let them out this morning and gave them fresh water and food, I then went to get them some fresh water to make sure they had cool water around 5pm when the heat index was still 110 outside. I found 2 of my BSL pullets and one of my EE roosters dead outside the run, they were still in the extended part but were not in the actual run where the water is, they were dead right outside the fence by the waterer so they could literally see it but could not reach it. I feel so bad right now to know that I caused this, I am really mad that I did not think about this happening. I buried the birds along with my pride, I also put 2 different waterers in that extended part, and an extra one in their coop so now they have 4 waterers and 2 feeders, it might be more than what they need but I feel I caused this so I must make it right for the future flock. I have only one pullet laying now I have several RIR, BR, and BSL chicks that are between 6 and 10 weeks old so I have a couple months before I am "back in the eggs" but perhaps that is the lesson I learn by not thinking about things so simple SO the lesson is, if you are placing your chickens or other animals outside their "normal enclosure" be sure to provide them with plenty of water and shade.