August in New Ulm is the sunniest month of the year. In August, the weather in New Ulm is typically warm. Average daily high temperature in August is about 26 degrees above zero. On average, New Ulm has 22 sunny, 6 partly cloudy, and 3 rainy days in August. The rains are usually heavy. August as well as July and September is considered the most comfortable time to visit New Ulm.