January in Thunder Bay is the windiest, the cloudiest, and the most freezing month of the year. In January, the weather in Thunder Bay is typically freezing. Average daily high temperature in January is about 9 degrees below zero. On average, Thunder Bay has 21 cloudy, 4 snowy, 3 sunny, and 3 partly cloudy days in January. The snowfalls are usually light. January as well as February, April, May, and October is considered the most uncomfortable time to visit Thunder Bay.