In September, the weather in Mar del Plata is typically warm. Average daily high temperature in September is about 15 degrees above zero. On average, Mar del Plata has 10 sunny, 8 partly cloudy, 7 rainy, and 5 cloudy days in September. The rains are usually heavy. September as well as June, July, August, and October is considered the most uncomfortable time to visit Mar del Plata.