With colder weather, decomposition is still taking place, it just slows down. The interior of the pile is warmer than the edges so aerating the compost heap by turning it is not recommended as this will cool down the whole pile. If desired, you can put a layer of straw or even a tarp over the pile to capture the heat from the pile. You may notice the compost pile freezing and thawing during the cold season. Though decomposition may not be efficient during that time, this process actually does help to break down the materials and provide more surface area for bacteria to do their job when the weather warms up again.
Adding food scraps to the compost pile can cause issues since it will not decompose very quickly. This can cause odors and attract pests to the heap. To avoid this, as you add food waste add a layer of dried leaves as well to maintain the carbon to nitrogen (green to brown) ratio. Also, be sure to bury the food scraps several inches into the compost heap. When the weather warms up, thoroughly turn the pile to incorporate the food scraps.
Smaller compost heaps do not generate as much heat as larger piles, so if you are heading into winter with a pile smaller than one cubic yard you may consider limiting the amount of food scraps you add during the winter months.
Cynthia Domenghini, Extension Agent