April in Oshkosh is the windiest month of the year. In April, the weather in Oshkosh is typically warm. Average daily high temperature in April is about 13 degrees above zero. On average, Oshkosh has 10 rainy, 9 sunny, 9 partly cloudy, and 2 cloudy days in April. The rains are usually heavy. April as well as February, March, October, and November is considered the most uncomfortable time to visit Oshkosh.