December in Bay City is the cloudiest month of the year. In December, the weather in Bay City is typically warm. Average daily high temperature in December is about 17 degrees above zero. On average, Bay City has 12 rainy, 10 sunny, 5 cloudy, and 4 partly cloudy days in December. The rains are usually moderate. December as well as June, July, August, and September is considered the most uncomfortable time to visit Bay City.