Even in chilly weather, the pile will get warm as the microbes chomp away. You may even see steam rising from it—this is normal. Ideally, the pile's internal temperature should be between 105 and 145 degrees F. You can use an elongated soil thermometer to take its temperature. A too-hot pile should be aerated, and it may need more material. If the pile is too cool, it may benefit from a sprinkling of packaged compost starter, available at garden centers. The starter provides an added dose of microbes; use it anytime decomposition slows down.