Everything I've read about worm composting says that the worms don't like it under 40 degrees

[HopeHoops]

3. They can dig down 2' or more to avoid the cold. Worm composting works best in the house, like under

the kitchen sink or in the basement. They're amazingly efficient. I've got outdoor compost bins and I toss a lot of worms in with the mix. They break it down very quickly and the bins are a thick black plastic so they actually stay pretty warm even in the coldest weather. I'm not sure what you have them in, but if there's a clear path to the natural soil under it they will just dig down and come back up in the spring.