Janesville, IL Weather & Growing Conditions
Tonight
57°F
Rain
Rain before 2am, then rain showers likely. Mostly cloudy, with a low around 57. South wind 14 to 18 mph, with gusts as high as 29 mph. Chance of precipitation is 90%. New rainfall amounts between a half and three quarters of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 57°F | Rain | 14 to 18 mph S | 94% |
| Wednesday | 63°F | Slight Chance Rain Showers then Mostly Cloudy | 9 to 14 mph SSW | 21% |
| Wednesday Night | 44°F | Partly Cloudy | 7 mph SW | 0% |
| Thursday | 63°F | Sunny | 7 to 13 mph WSW | 1% |
| Thursday Night | 44°F | Mostly Cloudy | 5 mph WNW | 4% |
| Friday | 56°F | Partly Sunny | 5 to 9 mph NNW | 12% |
| Friday Night | 38°F | Partly Cloudy | 7 mph NNW | 6% |
| Saturday | 54°F | Mostly Sunny | 5 mph NW | 1% |
| Saturday Night | 34°F | Partly Cloudy | 2 mph WNW | 1% |
| Sunday | 60°F | Sunny | 2 to 8 mph WNW | 9% |
| Sunday Night | 34°F | Mostly Clear | 5 mph NW | 6% |
| Monday | 63°F | Sunny | 3 to 9 mph WSW | 4% |
| Monday Night | 39°F | Mostly Clear | 6 mph WSW | 1% |
| Tuesday | 66°F | Sunny | 7 mph W | 1% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Janesville, IL
Last spring frost
Apr 15
First fall frost
Oct 24
Growing season
189 days
Hardiness zone
6a
Explore more for Janesville, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Mattoon Coles Co Ap, Il (5.9 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.