January in Arrochar is the cloudiest and the coldest month of the year. In January, the weather in Arrochar is typically cold. Average daily high temperature in January is about 4 degrees above zero. On average, Arrochar has 28 rainy, 2 sunny, and 1 cloudy day in January. The rains are usually heavy. January as well as February, March, April, and May is considered the most uncomfortable time to visit Arrochar.