August in Guaymas is the cloudiest and the hottest month of the year. In August, the weather in Guaymas is typically hot. Average daily high temperature in August is about 35 degrees above zero. On average, Guaymas has 14 sunny, 11 partly cloudy, 4 rainy, and 2 cloudy days in August. The rains are usually light. August as well as July and September is considered the most uncomfortable time to visit Guaymas.