Illiopolis, IL Weather Forecast
Local 7-day forecast
Chance Rain Showers
Track current conditions, temperature changes, wind, and the full daily outlook for Illiopolis, IL in one place.
A chance of rain showers. Mostly sunny. High near 57, with temperatures falling to around 52 in the afternoon. West northwest wind around 21 mph, with gusts as high as 29 mph. Chance of precipitation is 50%. New rainfall amounts between a quarter and half of an inch possible.
Local Weather Overview
This forecast page for Illiopolis, IL is designed for quick trip planning, giving you a clean read on daytime highs, overnight lows, and changing conditions across the upcoming forecast window. Latest sync: Apr 16, 2026 8:17 PM CDT.
The active forecast window currently covers Apr 18 to Apr 23, 2026 for Illiopolis, IL.
Page Snapshot
- Page focus
- city weather
- Forecast window
- Apr 18 to Apr 23, 2026
- Latest sync
- Apr 16, 2026 8:17 PM CDT
- Forecast office
- ILX
- Source
- NOAA / NWS
Daily Outlook
This Week in Illiopolis
Thursday looks like the warmest upcoming period in Illiopolis at 78 degrees F.
Saturday Night is the coolest period ahead with temperatures near 37 degrees F.
The strongest winds are forecast for Saturday at about 21 mph WNW.
Precipitation is mentioned in 4 upcoming forecast periods.
Forecast Details
- Last updated
- Apr 16, 2026 8:17 PM CDT
- Coverage
- 6 days
- Time zone
- America/Chicago
- Forecast office
- ILX
- Radar station
- KILX
Weather data is provided by the National Weather Service and refreshed automatically for U.S. locations.
Open NOAA sourceExtended Forecast
A slight chance of rain showers before 7pm, then patchy frost. Mostly clear, with a low around 37. West northwest wind 9 to 18 mph, with gusts as high as 26 mph. New rainfall amounts less than a tenth of an inch possible.
Patchy frost before 8am. Sunny, with a high near 59. West northwest wind 9 to 18 mph, with gusts as high as 26 mph.
Patchy frost after 3am. Mostly clear, with a low around 38. Northeast wind 6 to 13 mph, with gusts as high as 21 mph.
Patchy frost before 8am. Sunny, with a high near 67.
Mostly clear, with a low around 50.
Mostly sunny, with a high near 77.
Partly cloudy, with a low around 56.
Mostly sunny, with a high near 77.
A slight chance of rain showers after 1am. Mostly clear, with a low around 54.
A slight chance of rain showers before 1pm, then a slight chance of showers and thunderstorms. Mostly sunny, with a high near 78.
Detailed Forecast
| Period | Conditions | Temp | Wind |
|---|---|---|---|
|
Saturday
Apr 18
|
Chance Rain Showers
|
57°F |
21 mph
WNW
|
|
Saturday Night
Apr 18
|
Slight Chance Rain Showers then Patchy Frost
|
37°F |
9 to 18 mph
WNW
|
|
Sunday
Apr 19
|
Patchy Frost then Sunny
|
59°F |
9 to 18 mph
WNW
|
|
Sunday Night
Apr 19
|
Mostly Clear then Patchy Frost
|
38°F |
6 to 13 mph
NE
|
|
Monday
Apr 20
|
Patchy Frost then Sunny
|
67°F |
6 to 12 mph
SE
|
|
Monday Night
Apr 20
|
Mostly Clear
|
50°F |
10 to 14 mph
S
|
|
Tuesday
Apr 21
|
Mostly Sunny
|
77°F |
14 to 20 mph
SW
|
|
Tuesday Night
Apr 21
|
Partly Cloudy
|
56°F |
10 to 15 mph
SW
|
|
Wednesday
Apr 22
|
Mostly Sunny
|
77°F |
12 mph
SW
|
|
Wednesday Night
Apr 22
|
Mostly Clear then Slight Chance Rain Showers
|
54°F |
10 mph
SSE
|
|
Thursday
Apr 23
|
Slight Chance Rain Showers then Slight Chance Showers And Thunderstorms
|
78°F |
10 to 15 mph
SSE
|
Nearby Forecasts
Explore weather pages for nearby cities and major places around Illiopolis.