Etes,
It all depends on where the compost bin is located. If it's out in the full sun the conditions in the compost pile could get too hot for the worms and they might crawl away. If you've got a cellar you'd be better off putting a worm bin in there and composting indoors.
Kurt

Is your bin open on the bottom? I put a dozen Euros in my compost pile, as an experiment, and when I stir up the materials, they appear to be larger, and more active than my bin worms. Of course, I do have a large supply of horse manure, which I believe is their favorite food. So, if they can crawl down to escape the heat, I would think they'd be ok.