Extreme Heat Warning — Jefferson, IL, Wayne, IL, Edwards, IL, Wabash, IL, Perry, IL, Franklin, IL, Hamilton, IL, White, IL, Jackson, IL, Williamson, IL, Saline, IL, Gallatin, IL, Union, IL, Johnson, IL, Pope, IL, Hardin, IL, Alexander, IL, Pulaski, IL, Massac, IL, Gibson, IN, Pike, IN, Posey, IN, Vanderburgh, IN, Warrick, IN, Spencer, IN, Fulton, KY, Hickman, KY, Carlisle, KY, Ballard, KY, McCracken, KY, Graves, KY, Livingston, KY, Marshall, KY, Calloway, KY, Crittenden, KY, Lyon, KY, Trigg, KY, Caldwell, KY, Union, KY, Webster, KY, Hopkins, KY, Christian, KY, Henderson, KY, Daviess, KY, McLean, KY, Muhlenberg, KY, Todd, KY, Perry, MO, Bollinger, MO, Cape Girardeau, MO, Wayne, MO, Carter, MO, Ripley, MO, Butler, MO, Stoddard, MO, Scott, MO, Mississippi, MO, New Madrid, MO 8:00 PM

Williamson County, Illinois, United States

Last updated: 2:26 AM CDT  ·  Refresh
26°C
Feels like 29°
Clear
▲ 38°  /  ▼ 24°
Wind
2 mph S
Humidity
75%
Dew Point
22°
Pressure
29.47 inHg
Visibility
10 mi
UV Index
0.0
Cloud Cover
1%
Sunrise
6:28 AM
Sunset
7:20 PM
Drag to pan · double-click to forecast a point
WeatherAI™ Analysis

WeatherAI Analysis: Williamson County is currently clear at 26°C. Dry conditions are expected through the next 24 hours. Atmospheric instability is elevated (CAPE up to 1854 J/kg) — isolated convective development possible. Sunrise: 6:28AM · Sunset: 7:20PM.

Alerts

Extreme Heat Warning
Jefferson, IL, Wayne, IL, Edwards, IL, Wabash, IL, Perry, IL, Franklin, IL, Hamilton, IL, White, IL, Jackson, IL, Williamson, IL, Saline, IL, Gallatin, IL, Union, IL, Johnson, IL, Pope, IL, Hardin, IL, Alexander, IL, Pulaski, IL, Massac, IL, Gibson, IN, Pike, IN, Posey, IN, Vanderburgh, IN, Warrick, IN, Spencer, IN, Fulton, KY, Hickman, KY, Carlisle, KY, Ballard, KY, McCracken, KY, Graves, KY, Livingston, KY, Marshall, KY, Calloway, KY, Crittenden, KY, Lyon, KY, Trigg, KY, Caldwell, KY, Union, KY, Webster, KY, Hopkins, KY, Christian, KY, Henderson, KY, Daviess, KY, McLean, KY, Muhlenberg, KY, Todd, KY, Perry, MO, Bollinger, MO, Cape Girardeau, MO, Wayne, MO, Carter, MO, Ripley, MO, Butler, MO, Stoddard, MO, Scott, MO, Mississippi, MO, New Madrid, MO
Expires 8:00 PM
53 AQI · Moderate Dominant: PM2.5 Air Quality
Hourly Forecast · Next 24 Hours
Now
26°
10%
3 AM
26°
4%
4 AM
25°
12%
5 AM
23°
12%
6 AM
23°
12%
7 AM
24°
12%
8 AM
27°
12%
9 AM
31°
13%
10 AM
33°
18%
11 AM
34°
18%
12 PM
34°
18%
1 PM
37°
18%
2 PM
37°
19%
3 PM
37°
19%
4 PM
37°
23%
5 PM
38°
18%
6 PM
37°
18%
7 PM
35°
18%
8 PM
34°
18%
9 PM
28°
19%
10 PM
28°
19%
11 PM
28°
19%
12 AM
27°
19%
1 AM
28°
20%
7-Day Forecast
Today
38° 24°
Mostly Clear.
Sat
40° 24°
Partly Cloudy with a 41% chance of rain.
Sun
37° 18°
Mostly Clear.
Mon
34° 13°
Fog.
Tue
39° 17°
Clear.
Wed
41° 22°
Rain, 28% chance.
Thu
39° 19°
Clear.
TimeTempConditionsPrecipWindHumidity
Now 26° Clear 10% 2 mph S 75%
3 AM 26° Clear 4% 3 mph SSW 74%
4 AM 25° Clear 12% 3 mph SSW 75%
5 AM 23° Clear 12% 4 mph SSW 76%
6 AM 23° Clear 12% 4 mph S 78%
7 AM 24° Clear 12% 3 mph SSW 75%
8 AM 27° Clear 12% 3 mph SW 67%
9 AM 31° Clear 13% 4 mph WSW 57%
10 AM 33° Clear 18% 4 mph WSW 50%
11 AM 34° Clear 18% 4 mph WSW 45%
12 PM 34° Mostly Clear 18% 4 mph WSW 41%
1 PM 37° Mostly Clear 18% 4 mph SW 39%
2 PM 37° Mostly Clear 19% 5 mph SW 39%
3 PM 37° Mostly Clear 19% 5 mph SSW 38%
4 PM 37° Mostly Clear 23% 6 mph SSW 40%
5 PM 38° Mostly Clear 18% 5 mph SSW 43%
6 PM 37° Mostly Clear 18% 4 mph SSW 48%
7 PM 35° Mostly Clear 18% 4 mph S 53%
8 PM 34° Mostly Clear 18% 4 mph S 58%
9 PM 28° Mostly Clear 19% 5 mph S 62%
10 PM 28° Clear 19% 5 mph S 64%
11 PM 28° Mostly Clear 19% 4 mph S 66%
12 AM 27° Mostly Clear 19% 4 mph SSW 67%
1 AM 28° Mostly Clear 20% 4 mph SSW 68%
15-Day Forecast
Today
9/4
Mostly Clear
19%
24°
38°
Sat
9/5
Partly Cloudy
41%
24°
40°
Sun
9/6
Mostly Clear
13%
18°
37°
Mon
9/7
Fog
7%
13°
34°
Tue
9/8
Clear
3%
17°
39°
Wed
9/9
Rain
28%
22°
41°
Thu
9/10
Clear
17%
19°
39°
Fri
9/11
Rain
44%
16°
38°
Sat
9/12
Clear
19%
21°
42°
Sun
9/13
Clear
44%
17°
37°
Mon
9/14
Clear
60%
21°
38°
Tue
9/15
Drizzle
60%
22°
38°
Wed
9/16
Drizzle
60%
21°
37°
Thu
9/17
Drizzle
60%
19°
34°
Fri
9/18
Clear
25%
18°
34°
53
Moderate
U.S. Air Quality Index · Dominant: PM2.5
50 100 150 200

Air quality is acceptable. Unusually sensitive people should consider limiting prolonged outdoor exertion.

Pollutant Breakdown · Today
PM2.5
Fine particulate matter
Dominant
53 AQI 10.2 µg/m³
O3
Ground-level ozone
45 AQI 50 ppb
3-Day Outlook
DayAQICategoryO₃PM2.5
Today 53 Moderate 45 53
Sat 56 Moderate 44 56
Sun 55 Moderate 47 55
About the Air Quality Index
0–50 Good
51–100 Moderate
101–150 Unhealthy for Sensitive Groups
151–200 Unhealthy
201–300 Very Unhealthy
301–500 Hazardous

The U.S. AQI runs 0–500. The overall value equals the highest individual pollutant sub-index, and the dominant pollutant is the one driving it. PM2.5 (fine particles) is reported in µg/m³ and ozone (O3) in ppb. Forecast source: NWS NAQFC.

1000850700500400300250200150100 -40-30-20-10010203040 0.41247101624 LCLLFCEL0°C Temperature (°C) Pressure (hPa)
Temp Dewpoint Parcel (SB) CAPE CIN Dry adiabat Moist adiabat Mixing ratio
RAP
Valid Fri Sep 4, 06:00'Z' · F0 · 130 (13 km CONUS/NA)
Hodograph · kt
10 20 30 40 SM
0–1 1–3 3–6 6–9 km
Instability
SBCAPE331 J/kg
MLCAPE892 J/kg
MUCAPE1146 J/kg
SBCIN-422 J/kg
MLCIN-156 J/kg
Lifted Index-1.3
Kinematics
0–6 km Shear5 kt
0–1 km Shear10 kt
Eff. Shear5 kt
0–1 km SRH8
0–3 km SRH-5
Eff. SRH-10
Storm Motion9° @ 8 kt
0–1 km EHI0.0
Composite Parameters
Sig. Tornado0.0
STP (eff)0.0
Supercell0.0
K-Index36.9
Thermo & Levels
PWAT1.72 in
0–3 km LR5.2 °C/km
700–500 LR5.3 °C/km
Total Totals46.9
LCL941 hPa
LFC571 hPa
EL275 hPa
Freezing Lvl16,385 ft