April in Janesville averages a daily high of 14.5°C with nights around 2.1°C. Expect roughly 12.3 wet days totalling 89.3mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Janesville is May–September.
Based on AFTON JANESVILLE WWTP, WI US (6.3km), 1995–2024. 30 years of April data.