September in Barcelona is the rainiest and the cloudiest month of the year. In September, the weather in Barcelona is typically warm. Average daily high temperature in September is about 24 degrees above zero. On average, Barcelona has 13 rainy, 10 sunny, 6 partly cloudy, and 1 cloudy day in September. The rains are usually heavy. September as well as January, February, March, and April is considered the most uncomfortable time to visit Barcelona.