Most cars have air conditioning (a lot of trains do too), and most people commute well before and after the hottest part of the day. If your office is a sauna for three months and you won't fix it, everyone who isn't unemployable will probably quit.
That’s the same as asking, “Who would seriously just switch jobs because of more money?”
It’s a quality of living thing. If you don’t loose anything but can gain something, why not do it?
I mean if your job only allowed you to sit on a small unpadded stool, wouldn't that motivate you to find a new job?