April in Castlebar is the sunniest month of the year. In April, the weather in Castlebar is typically warm. Average daily high temperature in April is about 10 degrees above zero. On average, Castlebar has 17 rainy, 7 cloudy, 4 sunny, and 2 partly cloudy days in April. The rains are usually moderate. April as well as January, February, March, and May is considered the most uncomfortable time to visit Castlebar.