August in Cotulla is the hottest month of the year. In August, the weather in Cotulla is typically hot. Average daily high temperature in August is about 35 degrees above zero. On average, Cotulla has 18 sunny, 10 partly cloudy, and 3 rainy days in August. The rains are usually heavy. August as well as May, June, July, and September is considered the most uncomfortable time to visit Cotulla.