January in Pasadena is the rainiest and the cloudiest month of the year. In January, the weather in Pasadena is typically warm. Average daily high temperature in January is about 15 degrees above zero. On average, Pasadena has 15 sunny, 12 partly cloudy, and 4 rainy days in January. The rains are usually moderate. January as well as December is considered the most uncomfortable time to visit Pasadena.