In December, the weather in Biarritz is typically warm. Average daily high temperature in December is about 11 degrees above zero. On average, Biarritz has 15 rainy, 8 sunny, 7 partly cloudy, and 1 cloudy day in December. The rains are usually moderate. December as well as January, February, March, and November is considered the most uncomfortable time to visit Biarritz.