January in Dehiwala-Mount Lavinia is the sunniest month of the year. In January, the weather in Dehiwala-Mount Lavinia is typically hot. Average daily high temperature in January is about 28 degrees above zero. On average, Dehiwala-Mount Lavinia has 11 partly cloudy, 9 rainy, 9 sunny, and 2 cloudy days in January. The rains are usually heavy.