September in Sunny Isles Beach is the rainiest and the cloudiest month of the year. In September, the weather in Sunny Isles Beach is typically hot. Average daily high temperature in September is about 29 degrees above zero. On average, Sunny Isles Beach 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 Sunny Isles Beach.