April in Sioux Falls is the windiest month of the year. In April, the weather in Sioux Falls is typically warm. Average daily high temperature in April is about 13 degrees above zero. On average, Sioux Falls has 10 partly cloudy, 9 rainy, 7 sunny, and 4 cloudy days in April. The rains are usually moderate. April as well as March, May, and November is considered the most uncomfortable time to visit Sioux Falls.