December in Sveti Vlas is the windiest month of the year. In December, the weather in Sveti Vlas is typically cold. Average daily high temperature in December is about 8 degrees above zero. On average, Sveti Vlas has 10 rainy, 10 partly cloudy, 9 sunny, and 2 cloudy days in December. The rains are usually moderate. December as well as January, February, and March is considered the most uncomfortable time to visit Sveti Vlas.