August in Mazatlan is the rainiest, the cloudiest, and the hottest month of the year. In August, the weather in Mazatlan is typically hot. Average daily high temperature in August is about 30 degrees above zero. On average, Mazatlan has 23 rainy, 6 sunny, and 2 partly cloudy days in August. The rains are usually heavy. August as well as September is considered the most uncomfortable time to visit Mazatlan.