I must admit that, as far as being lucky, when it comes to weather I am extremely well-off. The San Francisco Bay Area has very mild weather compared with a lot of the rest of the country, and it makes growing and maintaining worms quite easy.
With the seasons moving on, however, I know a lot of you out there are staring down the first snowfall of the season and perhaps wondering how you can possibly take your summertime hobby of worm composting and bring it through the long, cold winter. Red worms thrive in temperatures (the temperature of the bedding, not the air) of between 55 and 77 degrees, but can survive perhaps 15-20 degrees beyond that in either direction depending on the circumstances. For you in cold locales wishing to practice worm composting all winter I have a couple of suggestions.
First, and most obvious, is to bring your worm composting bin inside. A garage or basement will suffice and will be several degrees higher than outdoors. That, in addition to the active decomposition of food (which produces heat) will keep your red wigglers happy and warm (enough) through the cold season. When in doubt, take the temperature of the bin. If it’s too low (below 55) then perhaps add a breathable blanket to help insulate and feed a little bit more (don’t forget the bedding!) to increase microbial activity and heat within the bin. Also, when moving a bin indoors don’t forget to cover it with a thin, breathable sheet to keep flies from becoming a nuisance.
Another more adventurous option is to experiment with your worm composting efforts outside, even in frigid weather. With a bit of planning and some manure to help keep things heated you can be successful. Remember, snow is insulating, so use that to your advantage. Dig a trench about 18″ deep and 18″ wide (do it soon, before the ground freezes!). Begin to fill it with horse manure and food scraps, at least 2′ long worth, and add your worms. Cover with a generous application of straw, about a foot deep. Make sure to cover the food well with the manure and straw; while many critters are hibernating during the cold season, you still don’t want to take your chances by leaving a free meal readily available to them. As the season progresses, add to the trench lengthwise your food scraps and more manure (the manure serves as bedding as well as food for the worms). Take the temperature frequently. And remember, if the whole thing goes kablooey, worms lay eggs that can survive through extremely tough weather; any worms you may lose during the winter will come back in the spring in the form of tiny hatchlings and start the work again.