Janesville, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Janesville, a community in Coles County, Illinois.
Today
85°F
Patchy Fog then Sunny
Patchy fog before 9am. Sunny, with a high near 85. South southeast wind 1 to 5 mph.
7-day forecast for Janesville
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 85°F | Patchy Fog then Sunny | 1 to 5 mph SSE | 0% |
| Tonight | 65°F | Mostly Clear | 3 mph SSE | 0% |
| Wednesday | 85°F | Sunny | 5 mph S | 1% |
| Wednesday Night | 67°F | Partly Cloudy then Chance Showers And Thunderstorms | 5 mph S | 35% |
| Thursday | 83°F | Showers And Thunderstorms Likely | 6 mph SSW | 66% |
| Thursday Night | 67°F | Chance Showers And Thunderstorms | 5 mph S | 38% |
| Friday | 83°F | Chance Showers And Thunderstorms | 5 mph SSW | 25% |
| Friday Night | 67°F | Slight Chance Showers And Thunderstorms | 3 mph SSW | 20% |
| Saturday | 85°F | Slight Chance Showers And Thunderstorms | 5 mph SSW | 19% |
| Saturday Night | 69°F | Slight Chance Showers And Thunderstorms then Mostly Clear | 6 mph SSW | 17% |
| Sunday | 87°F | Sunny | 6 to 9 mph SSW | 8% |
| Sunday Night | 71°F | Mostly Clear | 8 mph SSW | 8% |
| Monday | 88°F | Mostly Sunny | 9 mph SW | 11% |
| Monday Night | 71°F | Slight Chance Showers And Thunderstorms | 8 mph SSW | 24% |
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 Aug 4, 2026.