In December, the weather in Trbovlje is typically cold. Average daily high temperature in December is about 3 degrees above zero. On average, Trbovlje has 9 partly cloudy, 7 rainy, 7 sunny, 7 cloudy, and 1 snowy day in December. The rains are usually heavy. December as well as January, February, and November is considered the most uncomfortable time to visit Trbovlje.