December in Onchan is the rainiest and the windiest month of the year. In December, the weather in Onchan is typically cold. Average daily high temperature in December is about 9 degrees above zero. On average, Onchan has 26 rainy, 3 sunny, 1 cloudy, and 1 partly cloudy day in December. The rains are usually heavy. December as well as January, February, March, and May is considered the most uncomfortable time to visit Onchan.