April in Cornwall is the windiest month of the year. In April, the weather in Cornwall is typically warm. Average daily high temperature in April is about 12 degrees above zero. On average, Cornwall has 10 rainy, 9 partly cloudy, 7 sunny, and 4 cloudy days in April. The rains are usually heavy. April as well as March, October, November, and December is considered the most uncomfortable time to visit Cornwall.