September in Cotulla is the rainiest month of the year. In September, the weather in Cotulla is typically hot. Average daily high temperature in September is about 31 degrees above zero. On average, Cotulla has 16 sunny, 10 rainy, 3 partly cloudy, and 1 cloudy day in September. The rains are usually moderate. September as well as May, June, July, and August is considered the most uncomfortable time to visit Cotulla.