Janesville, WI Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Janesville, a city in Rock County, Wisconsin.
Today
84°F
Mostly Sunny
Mostly sunny, with a high near 84. Southwest wind 5 to 10 mph.
7-day forecast for Janesville
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 84°F | Mostly Sunny | 5 to 10 mph SW | 14% |
| Tonight | 64°F | Chance Showers And Thunderstorms then Showers And Thunderstorms | 5 to 10 mph W | 91% |
| Wednesday | 75°F | Patchy Fog | 5 mph W | 73% |
| Wednesday Night | 59°F | Chance Showers And Thunderstorms | 0 to 5 mph NW | 45% |
| Thursday | 78°F | Chance Rain Showers then Mostly Sunny | 0 to 5 mph NE | 25% |
| Thursday Night | 58°F | Mostly Clear | 0 mph | 9% |
| Friday | 81°F | Mostly Sunny | 0 to 5 mph S | 2% |
| Friday Night | 62°F | Mostly Clear | 0 to 5 mph S | 5% |
| Saturday | 83°F | Mostly Sunny | 5 to 10 mph SW | 12% |
| Saturday Night | 67°F | Slight Chance Showers And Thunderstorms | 5 to 10 mph SW | 27% |
| Sunday | 85°F | Chance Showers And Thunderstorms | 5 to 10 mph SW | 27% |
| Sunday Night | 66°F | Chance Showers And Thunderstorms | 5 to 10 mph SW | 46% |
| Monday | 83°F | Chance Rain Showers | 5 to 10 mph S | 45% |
| Monday Night | 66°F | Chance Showers And Thunderstorms | 5 mph NW | 44% |
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 Aug 4, 2026.