December in Glasgow is the windiest month of the year. In December, the weather in Glasgow is typically cold. Average daily high temperature in December is about 5 degrees above zero. On average, Glasgow has 25 rainy, 4 sunny, 1 cloudy, and 1 partly cloudy day in December. The rains are usually heavy. December as well as January, February, March, and April is considered the most uncomfortable time to visit Glasgow.