January in San Sebastian is the cloudiest and the coldest month of the year. In January, the weather in San Sebastian is typically cold. Average daily high temperature in January is about 9 degrees above zero. On average, San Sebastian has 19 rainy, 6 sunny, 4 partly cloudy, and 2 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.