September in San Andres is the hottest month of the year. In September, the weather in San Andres is typically hot. Average daily high temperature in September is about 29 degrees above zero. On average, San Andres has 23 rainy, 5 sunny, and 2 partly cloudy days in September. The rains are usually heavy. September as well as May, June, July, and August is considered the most uncomfortable time to visit San Andres.