Illinois City, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Illinois City, a community in Rock Island County, Illinois.
Today
86°F
Mostly Sunny
Mostly sunny, with a high near 86. Southwest wind 5 to 10 mph.
7-day forecast for Illinois City
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 86°F | Mostly Sunny | 5 to 10 mph SW | 12% |
| Tonight | 68°F | Chance Showers And Thunderstorms | 5 mph NE | 79% |
| Wednesday | 79°F | Showers And Thunderstorms then Showers And Thunderstorms Likely | 5 mph NE | 81% |
| Wednesday Night | 63°F | Showers And Thunderstorms Likely | 0 to 5 mph N | 74% |
| Thursday | 81°F | Chance Rain Showers then Mostly Sunny | 5 mph NE | 45% |
| Thursday Night | 63°F | Mostly Clear | 0 to 5 mph NE | 6% |
| Friday | 83°F | Mostly Sunny | 0 to 5 mph SE | 5% |
| Friday Night | 66°F | Mostly Clear | 0 to 5 mph S | 12% |
| Saturday | 86°F | Sunny | 5 mph S | 10% |
| Saturday Night | 71°F | Mostly Clear | 5 to 10 mph S | 14% |
| Sunday | 88°F | Sunny | 10 mph S | 14% |
| Sunday Night | 71°F | Slight Chance Showers And Thunderstorms | 5 to 10 mph S | 31% |
| Monday | 87°F | Chance Showers And Thunderstorms then Slight Chance Showers And Thunderstorms | 5 to 10 mph S | 31% |
| Monday Night | 71°F | Chance Showers And Thunderstorms | 10 mph S | 32% |
Forecast source: National Weather Service (api.weather.gov) for Illinois City (41.399, -90.900). Updated through the day.
Growing snapshot for Illinois City
Last spring frost
Apr 18
First fall frost
Oct 24
Growing season
188 days
Hardiness zone
5b
More local growing data for Illinois City: nearby ZIP 61259 weather · frost dates · planting calendar · Illinois frost dates
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Climate data from the nearest NOAA station, Illinois City Dam 16, Il (5.2 mi from Illinois City). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.