Koster, IL Weather Forecast
Local 7-day forecast
Chance Showers And Thunderstorms
Track current conditions, temperature changes, wind, and the full daily outlook for Koster, IL in one place.
A chance of showers and thunderstorms. Partly sunny, with a high near 86. South southwest wind 5 to 10 mph. Chance of precipitation is 50%.
Local Weather Overview
This forecast page for Koster, 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: Jun 7, 2026 5:45 PM CDT.
The active forecast window currently covers Jun 9 to Jun 13, 2026 for Koster, IL.
Page Snapshot
- Page focus
- city weather
- Forecast window
- Jun 9 to Jun 13, 2026
- Latest sync
- Jun 7, 2026 5:45 PM CDT
- Forecast office
- LOT
- Source
- NOAA / NWS
Daily Outlook
This Week in Koster
Wednesday looks like the warmest upcoming period in Koster at 90 degrees F.
Thursday Night is the coolest period ahead with temperatures near 62 degrees F.
The strongest winds are forecast for Wednesday at about 10 to 15 mph SSW.
Precipitation is mentioned in 10 upcoming forecast periods.
Forecast Details
- Last updated
- Jun 7, 2026 5:45 PM CDT
- Coverage
- 5 days
- Time zone
- America/Chicago
- Forecast office
- LOT
- Radar station
- KLOT
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 a chance of showers and thunderstorms. Partly cloudy, with a low around 73. Chance of precipitation is 30%.
A chance of showers and thunderstorms before 7am. Sunny, with a high near 90.
A chance of showers and thunderstorms after 7pm. Partly cloudy, with a low around 71.
A chance of showers and thunderstorms. Mostly sunny, with a high near 90.
A chance of showers and thunderstorms before 7pm, then showers and thunderstorms likely. Mostly cloudy, with a low around 62.
A chance of rain showers before 7am. Mostly sunny, with a high near 86.
A slight chance of rain showers after 7pm. Mostly clear, with a low around 62.
A slight chance of rain showers before 7am, then a slight chance of showers and thunderstorms. Mostly sunny, with a high near 88.
A chance of showers and thunderstorms before 1am, then a chance of showers and thunderstorms. Partly cloudy, with a low around 63.
Detailed Forecast
| Period | Conditions | Temp | Wind |
|---|---|---|---|
|
Tuesday
Jun 9
|
Chance Showers And Thunderstorms
|
86°F |
5 to 10 mph
SSW
|
|
Tuesday Night
Jun 9
|
Chance Showers And Thunderstorms
|
73°F |
5 to 10 mph
SSW
|
|
Wednesday
Jun 10
|
Chance Showers And Thunderstorms then Sunny
|
90°F |
10 to 15 mph
SSW
|
|
Wednesday Night
Jun 10
|
Chance Showers And Thunderstorms
|
71°F |
10 to 15 mph
SSW
|
|
Thursday
Jun 11
|
Chance Showers And Thunderstorms
|
90°F |
10 to 15 mph
SW
|
|
Thursday Night
Jun 11
|
Chance Showers And Thunderstorms then Showers And Thunderstorms Likely
|
62°F |
5 to 10 mph
WSW
|
|
Friday
Jun 12
|
Chance Rain Showers then Mostly Sunny
|
86°F |
5 to 10 mph
W
|
|
Friday Night
Jun 12
|
Slight Chance Rain Showers
|
62°F |
0 to 5 mph
SW
|
|
Saturday
Jun 13
|
Slight Chance Rain Showers then Slight Chance Showers And Thunderstorms
|
88°F |
5 to 10 mph
SSW
|
|
Saturday Night
Jun 13
|
Chance Showers And Thunderstorms
|
63°F |
5 mph
SW
|
Nearby Forecasts
Explore weather pages for nearby cities and major places around Koster.