Posen, IL Weather & Growing Conditions
Today
85°F
Mostly Sunny
Mostly sunny, with a high near 85. South southwest wind 5 to 10 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 85°F | Mostly Sunny | 5 to 10 mph SSW | 3% |
| Tonight | 68°F | Mostly Cloudy | 5 mph SSW | 9% |
| Wednesday | 82°F | Slight Chance Showers And Thunderstorms | 5 mph SW | 52% |
| Wednesday Night | 66°F | Showers And Thunderstorms | 5 mph WSW | 87% |
| Thursday | 78°F | Rain Showers then Chance Showers And Thunderstorms | 0 to 5 mph SSE | 86% |
| Thursday Night | 64°F | Chance Showers And Thunderstorms then Partly Cloudy | 0 to 5 mph SE | 39% |
| Friday | 82°F | Mostly Sunny | 0 to 5 mph SSW | 6% |
| Friday Night | 66°F | Partly Cloudy | 0 to 5 mph S | 8% |
| Saturday | 84°F | Mostly Sunny | 0 to 5 mph SSW | 10% |
| Saturday Night | 70°F | Partly Cloudy then Slight Chance Showers And Thunderstorms | 5 mph SSW | 16% |
| Sunday | 86°F | Slight Chance Showers And Thunderstorms then Mostly Sunny | 5 to 10 mph SW | 16% |
| Sunday Night | 71°F | Chance Showers And Thunderstorms | 5 to 10 mph SW | 41% |
| Monday | 86°F | Chance Rain Showers | 5 to 10 mph SW | 41% |
| Monday Night | 70°F | Chance Showers And Thunderstorms | 5 to 10 mph WSW | 47% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Posen, IL
Last spring frost
Apr 10
First fall frost
Nov 1
Growing season
203 days
Hardiness zone
6a
Explore more for Posen, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Chicago Midway Ap 3Sw, Il (8.8 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.