January in Terrance B. Lettsome International Airport is the coldest month of the year. In January, the weather in Terrance B. Lettsome International Airport is typically warm. Average daily high temperature in January is about 25 degrees above zero. On average, Terrance B. Lettsome International Airport has 15 rainy, 15 sunny, and 1 partly cloudy day in January. The rains are usually light.