January in Janesville averages a daily high of -2°C with nights around -10.9°C. Expect roughly 10.3 wet days totalling 43.1mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Janesville is May–September.
Based on AFTON JANESVILLE WWTP, WI US (6.3km), 1995–2024. 29 years of January data.