Janesville, WI Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Janesville, a city in Rock County, Wisconsin.
This Afternoon
69°F
Chance Rain Showers
A chance of rain showers. Mostly cloudy, with a high near 69. East wind around 15 mph. Chance of precipitation is 50%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Janesville
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 69°F | Chance Rain Showers | 15 mph E | 49% |
| Tonight | 60°F | Chance Showers And Thunderstorms | 10 mph E | 90% |
| Saturday | 73°F | Showers And Thunderstorms | 5 to 10 mph SE | 93% |
| Saturday Night | 60°F | Showers And Thunderstorms | 5 to 10 mph E | 79% |
| Sunday | 66°F | Chance Rain Showers | 10 to 15 mph NE | 54% |
| Sunday Night | 53°F | Chance Rain Showers then Mostly Cloudy | 10 to 15 mph NE | 36% |
| Monday | 62°F | Chance Rain Showers | 15 mph NE | 33% |
| Monday Night | 48°F | Chance Rain Showers | 10 to 15 mph NE | 33% |
| Tuesday | 61°F | Slight Chance Rain Showers then Mostly Cloudy | 10 to 15 mph NE | 19% |
| Tuesday Night | 47°F | Mostly Cloudy | 5 to 10 mph NE | 9% |
| Wednesday | 64°F | Partly Sunny | 5 to 10 mph NE | 6% |
| Wednesday Night | 48°F | Partly Cloudy | 0 to 5 mph NE | 2% |
| Thursday | 66°F | Partly Sunny | 0 to 5 mph NE | 6% |
| Thursday Night | 50°F | Partly Cloudy | 0 to 5 mph NE | 5% |
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 Sep 19, 2026.