September in San Leandro is the sunniest and the warmest month of the year. In September, the weather in San Leandro is typically warm. Average daily high temperature in September is about 25 degrees above zero. On average, San Leandro has 20 sunny, 9 partly cloudy, and 1 rainy day in September. The rains are usually light. September as well as June, July, August, and October is considered the most comfortable time to visit San Leandro.