April in Llanelli is the sunniest month of the year. In April, the weather in Llanelli is typically warm. Average daily high temperature in April is about 11 degrees above zero. On average, Llanelli has 13 rainy, 9 partly cloudy, 6 sunny, and 2 cloudy days in April. The rains are usually heavy. April as well as January, February, March, and May is considered the most uncomfortable time to visit Llanelli.