September in Boca Raton is the rainiest and the cloudiest month of the year. In September, the weather in Boca Raton is typically hot. Average daily high temperature in September is about 29 degrees above zero. On average, Boca Raton has 23 rainy and 7 sunny days in September. The rains are usually heavy. September as well as June, July, August, and October is considered the most uncomfortable time to visit Boca Raton.