If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in South Beloit: The hottest months are usually July and August with an average temp of 69°F, while the coldest months are January and February with an average of 27°F. The snowiest months in South Beloit are January, March, December, and April, with each month seeing an average of 6 inches of snowfall.