January in Carnac is the rainiest and the cloudiest month of the year. In January, the weather in Carnac is typically cold. Average daily high temperature in January is about 9 degrees above zero. On average, Carnac has 17 rainy, 5 sunny, 5 partly cloudy, and 4 cloudy days in January. The rains are usually heavy. January as well as February, November, and December is considered the most uncomfortable time to visit Carnac.