In April, the weather in Biarritz is typically warm. Average daily high temperature in April is about 14 degrees above zero. On average, Biarritz has 15 rainy, 7 sunny, 7 partly cloudy, and 1 cloudy day in April. The rains are usually heavy. April as well as January, February, March, and May is considered the most uncomfortable time to visit Biarritz.