August in Rostov-na-Donu is the sunniest and the hottest month of the year. In August, the weather in Rostov-na-Donu is typically hot. Average daily high temperature in August is about 30 degrees above zero. On average, Rostov-na-Donu has 28 sunny, 2 rainy, and 1 partly cloudy day in August. The rains are usually light.