December in Terrance B. Lettsome International Airport is the windiest month of the year. In December, the weather in Terrance B. Lettsome International Airport is typically warm. Average daily high temperature in December is about 27 degrees above zero. On average, Terrance B. Lettsome International Airport has 20 sunny, 9 rainy, and 2 partly cloudy days in December. The rains are usually light.