I can't speak for 5a, but the 6a I had got really warm doing pretty much anything irrespective of the weather outside. Without a doubt the hottest phone I ever had. I didn't think it would bother me but ended up returning it anyway. 10-minute long video calls caused the screen go black on several occasions. Holding out for Pixel 7 and hoping for a much cooler device. Some people don't seem to experience this issue or maybe just aren't bothered by it.