Composting isn't just for warm weather. It can be a year-round activity, which, in the winter months, allows you to compost "green" kitchen scraps and lots of coffee grounds for use on your roses in the spring. Even here in Minnesota, where the ground usually freezes hard and deep in winter, compost piles will generally remain mostly unfrozen beneath the snow because of the heat generated in the decomposition process. If you dig through the snow and open up holes in the pile, you can keep adding to it all winter. But that hasn't been necessary here this winter, as you can see in the picture below. Our low temperature in January was -11 f., which puts us almost in USDA Zone 6. We had a lot of days above freezing in late December and throughout January, and what little snow we had is just about gone.
As usual, some folks in Minnesota go to extremes. I heard a funny story in mid-November, when it was actually much colder and snowier than was in December and January. Someone, here in Minneapolis, had moved their composting operation into their basement for the winter, in one of those fancy (and expensive) rotating drums. I guess I was kind of incredulous and asked what they were going to do with it in the basement. The guy was kind of put out when I asked him why they just didn't leave it outside to compost naturally. I really can't imagine having that decomposition process going on in my basement. I just make a pile outside, where everything happens naturally, and the earthworms have a field day, leaving their castings (down deep where it's warm), year-round.
Today, I dumped about 200 lb. of Starbucks coffee grounds in my pile, along with lots of green kitchen scraps. When I opened up the pile, a cloud of steam puffed out; proof positive that the composting process is alive and well in mid-winter. Here's how it looked, after I finished pulling the shredded oak leaves back on top. Note the lack of snow and the two Christmas trees behind the pile doing double duty as a habitat for birds and other winter critters. The white stake in the foreground is a terminal post for my electric fence, which comes up from underground at that point for use in the summer. The small white stakes to the left, in the little bit of snow that's left, mark spots where I have seeded pollinating plants for stratification over the winter. This area around my mulch pile is one of several insectaries, designed to attract bees and other beneficial insects to my rose gardens. (See http://theminnesotarosegardener.blogspot.com/2014/12/bugs-and-roses.html ).