July in Mar del Plata is the coldest month of the year. In July, the weather in Mar del Plata is typically warm. Average daily high temperature in July is about 12 degrees above zero. On average, Mar del Plata has 13 partly cloudy, 10 sunny, 4 rainy, and 4 cloudy days in July. The rains are usually heavy. July as well as June, August, and September is considered the most uncomfortable time to visit Mar del Plata.