Janesville, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Janesville, a community in Coles County, Illinois.
Overnight
70°F
Mostly Cloudy
Mostly cloudy, with a low around 70. Southeast wind around 6 mph.
7-day forecast for Janesville
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 70°F | Mostly Cloudy | 6 mph SE | 12% |
| Saturday | 92°F | Partly Sunny then Chance Showers And Thunderstorms | 8 mph SW | 28% |
| Saturday Night | 70°F | Mostly Cloudy | 6 mph S | 7% |
| Sunday | 87°F | Mostly Sunny then Chance Showers And Thunderstorms | 3 to 9 mph NNW | 33% |
| Sunday Night | 62°F | Chance Showers And Thunderstorms | 12 mph NE | 61% |
| Monday | 72°F | Showers And Thunderstorms Likely | 13 mph NE | 70% |
| Monday Night | 55°F | Chance Showers And Thunderstorms then Slight Chance Showers And Thunderstorms | 9 to 14 mph NE | 52% |
| Tuesday | 68°F | Slight Chance Showers And Thunderstorms | 13 mph NNE | 26% |
| Tuesday Night | 53°F | Chance Showers And Thunderstorms then Mostly Cloudy | 7 to 12 mph NNE | 26% |
| Wednesday | 71°F | Mostly Sunny | 10 mph NNE | 6% |
| Wednesday Night | 54°F | Partly Cloudy | 5 to 9 mph N | 3% |
| Thursday | 72°F | Mostly Sunny | 9 mph N | 2% |
| Thursday Night | 55°F | Partly Cloudy | 5 to 8 mph NNE | 3% |
| Friday | 74°F | Mostly Sunny | 8 mph NNE | 2% |
Forecast source: National Weather Service (api.weather.gov) for Janesville (39.375, -88.245). Updated through the day.
Growing snapshot for Janesville
Last spring frost
Apr 15
First fall frost
Oct 24
Growing season
189 days
Hardiness zone
6a
More local growing data for Janesville: nearby ZIP 62440 weather · frost dates · planting calendar · Illinois frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Mattoon Coles Co Ap, Il (5.9 mi from Janesville). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.