September in Monterrey is the rainiest and the cloudiest month of the year. In September, the weather in Monterrey is typically warm. Average daily high temperature in September is about 27 degrees above zero. On average, Monterrey has 11 rainy, 11 sunny, and 8 partly cloudy days in September. The rains are usually moderate. September as well as {{month_nom: February}}, and {{month_nom: February}} is considered the most uncomfortable time to visit Monterrey.