December in Glendale is the coldest month of the year. In December, the weather in Glendale is typically warm. Average daily high temperature in December is about 14 degrees above zero. On average, Glendale has 17 sunny, 11 partly cloudy, and 3 rainy days in December. The rains are usually light. December as well as January is considered the most uncomfortable time to visit Glendale.