In December, the weather in Los Alamos is typically cold. Average daily high temperature in December is about 1 degree above zero. On average, Los Alamos has 11 partly cloudy, 10 sunny, 5 rainy, 4 cloudy, and 1 snowy day in December. The rains are usually light. December as well as January, February, and November is considered the most uncomfortable time to visit Los Alamos.