I am in Western PA next to the border of Eastern Ohio. Yes, I have successfully wintered over worms in an outside system. I was sort of aprehensive the first time I tried it because of the winters here. However, unlike you, I did not use raised beds. I bury my beds in the ground so that just the top is visible. I imagine that burying the bins, keeps the bedding temperature warmer in the winter and cooler in the summer. Another trick I did was I made sure I used plenty of hay/straw in the bedding. It tends to heat up quickly when placed with nitrogenic food substances. I also used a small amount of horse manure in the bedding. Large amounts of feed are used which also helps to heat up the bins. So, the combination of using straw, manure, and lots of food, and the fact that the bins are buried, allows my worms to thrive outside through the winter and stay warm enough. As a matter of fact, some of my best worms have come from the outside bin systems.

As for your raised beds, I cannot give you accurate advice. Without the bins being buried, they will be subjected too much more extreme temps. I have heard of people who have placed hay bails all around the outside of their raised beds. The hay bails act like an insulator.

Darryl