April in Oshkosh is the rainiest month of the year. In April, the weather in Oshkosh is typically warm. Average daily high temperature in April is about 10 degrees above zero. On average, Oshkosh has 13 rainy, 8 cloudy, 5 sunny, and 4 partly cloudy days in April. The rains are usually heavy. April as well as March and November is considered the most uncomfortable time to visit Oshkosh.