January in San Sebastian is the cloudiest month of the year. In January, the weather in San Sebastian is typically warm. Average daily high temperature in January is about 11 degrees above zero. On average, San Sebastian has 17 rainy, 7 partly cloudy, 4 sunny, and 3 cloudy days in January. The rains are usually heavy. January as well as February, March, April, and May is considered the most uncomfortable time to visit San Sebastian.