Illiopolis, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Illiopolis, a village in Sangamon County, Illinois.
Overnight
56°F
Slight Chance Light Rain
A slight chance of rain. Mostly cloudy, with a low around 56. South southwest wind around 13 mph, with gusts as high as 22 mph. Chance of precipitation is 20%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Illiopolis
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 56°F | Slight Chance Light Rain | 13 mph SSW | 23% |
| Wednesday | 60°F | Slight Chance Drizzle | 12 to 15 mph SW | 11% |
| Wednesday Night | 43°F | Slight Chance Drizzle then Mostly Cloudy | 12 mph WSW | 10% |
| Thursday | 61°F | Partly Sunny | 10 to 15 mph WSW | 10% |
| Thursday Night | 43°F | Mostly Cloudy | 5 to 9 mph NW | 5% |
| Friday | 54°F | Partly Sunny | 13 mph NNW | 5% |
| Friday Night | 33°F | Partly Cloudy | 2 to 9 mph NNW | 0% |
| Saturday | 53°F | Mostly Sunny | 2 to 6 mph NNW | 0% |
| Saturday Night | 32°F | Partly Cloudy | 3 mph NW | 1% |
| Sunday | 59°F | Sunny | 2 to 9 mph WNW | 1% |
| Sunday Night | 34°F | Clear | 1 to 5 mph W | 1% |
| Monday | 63°F | Sunny | 1 to 8 mph SW | 0% |
| Monday Night | 39°F | Clear | 6 mph SW | 0% |
| Tuesday | 66°F | Sunny | 6 mph WNW | 1% |
Forecast source: National Weather Service (api.weather.gov) for Illiopolis (39.850, -89.252). Updated through the day.
Growing snapshot for Illiopolis
Last spring frost
Apr 14
First fall frost
Oct 24
Growing season
192 days
Hardiness zone
6a
More local growing data for Illiopolis: nearby ZIP 62539 weather · frost dates · planting calendar · Illinois frost dates
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Climate data from the nearest NOAA station, Decatur Wtp, Il (16.1 mi from Illiopolis). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.