December in St.Lucia is the rainiest month of the year. In December, the weather in St.Lucia is typically warm. Average daily high temperature in December is about 26 degrees above zero. On average, St.Lucia has 16 rainy, 8 sunny, 4 partly cloudy, and 3 cloudy days in December. The rains are usually heavy. December as well as January, October, and November is considered the most uncomfortable time to visit St.Lucia.