In August, the weather in Haverfordwest is typically warm. Average daily high temperature in August is about 17 degrees above zero. On average, Haverfordwest has 21 rainy, 5 sunny, 3 partly cloudy, and 2 cloudy days in August. The rains are usually heavy. August as well as January, February, March, and July is considered the most uncomfortable time to visit Haverfordwest.