Janesville, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Janesville, a community in Coles County, Illinois.
Overnight
59°F
Light Rain
Rain. Cloudy, with a low around 59. South wind 13 to 16 mph, with gusts as high as 28 mph. Chance of precipitation is 100%. New rainfall amounts between a tenth and quarter of an inch possible.
7-day forecast for Janesville
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 59°F | Light Rain | 13 to 16 mph S | 96% |
| Wednesday | 63°F | Chance Light Rain then Mostly Cloudy | 10 to 14 mph SW | 29% |
| Wednesday Night | 46°F | Mostly Cloudy | 9 mph WSW | 4% |
| Thursday | 62°F | Mostly Sunny | 9 to 14 mph WSW | 3% |
| Thursday Night | 45°F | Mostly Cloudy | 5 mph WNW | 1% |
| Friday | 55°F | Partly Sunny | 6 to 10 mph NNW | 5% |
| Friday Night | 35°F | Partly Cloudy | 5 to 9 mph NNW | 0% |
| Saturday | 54°F | Sunny | 6 mph NNW | 0% |
| Saturday Night | 33°F | Partly Cloudy | 2 mph NW | 0% |
| Sunday | 59°F | Sunny | 2 to 8 mph WNW | 2% |
| Sunday Night | 34°F | Clear | 3 mph W | 0% |
| Monday | 63°F | Sunny | 2 to 6 mph SW | 0% |
| Monday Night | 39°F | Clear | 5 mph SW | 0% |
| Tuesday | 66°F | Sunny | 5 mph W | 1% |
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 Nov 4, 2026.