Janesville, WI Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Janesville, a city in Rock County, Wisconsin.
Today
59°F
Cloudy then Isolated Rain Showers
Isolated rain showers after 3pm. Cloudy. High near 59, with temperatures falling to around 53 in the afternoon. Southwest wind 10 to 15 mph.
7-day forecast for Janesville
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 59°F | Cloudy then Isolated Rain Showers | 10 to 15 mph SW | 13% |
| Tonight | 45°F | Slight Chance Rain Showers | 10 to 15 mph SW | 16% |
| Thursday | 54°F | Rain Showers Likely then Chance Light Rain | 10 to 15 mph W | 55% |
| Thursday Night | 38°F | Chance Light Rain then Mostly Cloudy | 10 mph N | 31% |
| Friday | 47°F | Partly Sunny | 5 to 15 mph N | 4% |
| Friday Night | 30°F | Partly Cloudy | 0 to 5 mph N | 0% |
| Saturday | 50°F | Sunny | 0 to 5 mph NW | 0% |
| Saturday Night | 32°F | Mostly Clear | 0 to 5 mph W | 0% |
| Sunday | 55°F | Sunny | 5 to 10 mph W | 5% |
| Sunday Night | 33°F | Mostly Clear | 0 to 5 mph W | 0% |
| Monday | 59°F | Sunny | 0 to 10 mph SW | 0% |
| Monday Night | 38°F | Mostly Clear | 5 to 10 mph W | 0% |
| Tuesday | 60°F | Sunny | 5 mph NW | 1% |
| Tuesday Night | 37°F | Partly Cloudy | 0 to 5 mph NW | 0% |
Forecast source: National Weather Service (api.weather.gov) for Janesville (42.685, -89.013). Updated through the day.
Growing snapshot for Janesville
Last spring frost
Apr 26
First fall frost
Oct 15
Growing season
170 days
Hardiness zone
5b
More local growing data for Janesville: nearby ZIP 53545 weather · frost dates · planting calendar · Wisconsin frost dates
Nearby towns & communities
Brodhead
Clinton
Edgerton
Evansville
Footville
Fulton
Hanover
Lake Koshkonong
Milton
Orfordville
Shopiere
Climate data from the nearest NOAA station, Afton - Janesville Wwtp, Wi (7.1 mi from Janesville). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.