"Bees" and warm engines

I’m using the term “bees” generically. It includes wasps & hornets.
I’ve noticed that they seem attracted to sources of heat. Whether it’s my car, motorcycle, or lawn mower, in the summer I always find a bee or two hovering around it if the engine is warm. Why? are they cold?

BUMP into the warm part of it.:wink:

Does it have to do with fumes, or the heat itself?