December in Palo Alto is the coldest month of the year. In December, the weather in Palo Alto is typically warm. Average daily high temperature in December is about 12 degrees above zero. On average, Palo Alto has 13 partly cloudy, 12 sunny, 5 rainy, and 1 cloudy day in December. The rains are usually light. December as well as January and February is considered the most uncomfortable time to visit Palo Alto.