December in San Jose is the coldest month of the year. In December, the weather in San Jose is typically warm. Average daily high temperature in December is about 11 degrees above zero. On average, San Jose has 13 partly cloudy, 11 sunny, 6 rainy, and 1 cloudy day in December. The rains are usually moderate. December as well as January and February is considered the most uncomfortable time to visit San Jose.