Unfortunately we do indeed have summers where it gets above freezing.

Like I said, it had gotten up to 85*F that day. Or maybe it was 80*F? Whatever it was, it felt miserable. The chickens made it through all right (the bantams were thrilled, the LF stayed in the shade and panted) but evidently it was too much for the cot. I haven't lost anything else to heat stroke in the ~200 I have had.
It felt rather warm and it was panting and on its side. Could have been something else but heat stroke is my best guess, given the temperature on that day.