The temperatures here don't normally get low enough to stop decomposition. Heat is generated in the centers of all these compost bins, so the bacteria and insects keep working. You don't need to turn the compost quite as often, but you should still keep adding fertilizer. A nitrogen, potassium, and phosphorus composition works best. The fertilizer is food for bacteria.
Air is also essential for many composting bacteria, so turning the pile is important.
If you work at your compost pile, you'll be ready to grow a great garden this spring. In real life, Dr. K is Museum President and CEO, Dr. Thomas Krakauer.