Severe Thunderstorm Watch 9:00 PM

Williamson County, Illinois, United States

Last updated: 8:36 PM CDT  ·  Refresh
28°C
Feels like 31°
Clear
▲ 34°  /  ▼ 19°
Wind
7 mph NNW
Humidity
75%
Dew Point
22°
Pressure
29.36 inHg
Visibility
10 mi
UV Index
0.0
Cloud Cover
10%
Sunrise
5:50 AM
Sunset
8:13 PM
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WeatherAI™ Analysis

WeatherAI Analysis: Williamson County is currently clear at 28°C. Dry conditions are expected through the next 24 hours. Atmospheric instability is elevated (CAPE up to 567 J/kg) — isolated convective development possible. Sunrise: 5:50AM · Sunset: 8:13PM.

Alerts

Severe Thunderstorm Watch
Expires 9:00 PM
43 AQI · Good Dominant: PM2.5 Air Quality
Hourly Forecast · Next 24 Hours
Now
28°
11%
9 PM
26°
14%
10 PM
25°
14%
11 PM
24°
14%
12 AM
23°
7%
1 AM
22°
3%
2 AM
21°
3%
3 AM
21°
3%
4 AM
20°
3%
5 AM
19°
3%
6 AM
19°
3%
7 AM
20°
3%
8 AM
22°
3%
9 AM
23°
3%
10 AM
24°
5%
11 AM
26°
5%
12 PM
26°
5%
1 PM
27°
5%
2 PM
27°
5%
3 PM
28°
5%
4 PM
28°
3%
5 PM
28°
3%
6 PM
27°
3%
7 PM
26°
3%
7-Day Forecast
Tonight
34° 19°
Clear.
Wed
29° 17°
Partly Cloudy.
Thu
27° 15°
Clear.
Fri
23° 16°
Overcast with a 62% chance of rain.
Sat
30° 18°
Partly Cloudy with a 45% chance of rain.
Sun
34° 23°
Clear.
Mon
34° 23°
Clear.
TimeTempConditionsPrecipWindHumidity
Now 28° Clear 11% 7 mph NNW 75%
9 PM 26° Clear 14% 8 mph N 79%
10 PM 25° Clear 14% 8 mph N 80%
11 PM 24° Clear 14% 7 mph N 82%
12 AM 23° Clear 7% 7 mph N 84%
1 AM 22° Clear 3% 6 mph NNW 86%
2 AM 21° Clear 3% 6 mph NNW 88%
3 AM 21° Clear 3% 6 mph NNW 90%
4 AM 20° Clear 3% 6 mph NNW 90%
5 AM 19° Clear 3% 6 mph NNW 90%
6 AM 19° Clear 3% 6 mph NNW 89%
7 AM 20° Clear 3% 7 mph N 86%
8 AM 22° Clear 3% 7 mph N 82%
9 AM 23° Clear 3% 8 mph NNE 77%
10 AM 24° Mostly Clear 5% 8 mph NNE 73%
11 AM 26° Partly Cloudy 5% 9 mph NNE 70%
12 PM 26° Partly Cloudy 5% 10 mph NNE 66%
1 PM 27° Mostly Cloudy 5% 10 mph NNE 63%
2 PM 27° Mostly Cloudy 5% 10 mph NNE 62%
3 PM 28° Mostly Cloudy 5% 10 mph NNE 61%
4 PM 28° Mostly Cloudy 3% 10 mph NNE 62%
5 PM 28° Mostly Cloudy 3% 10 mph NNE 65%
6 PM 27° Partly Cloudy 3% 9 mph NNE 68%
7 PM 26° Partly Cloudy 3% 9 mph NNE 70%
15-Day Forecast
Today
7/21
Clear
14%
19°
34°
Wed
7/22
Partly Cloudy
5%
17°
29°
Thu
7/23
Clear
3%
15°
27°
Fri
7/24
Overcast
62%
16°
23°
Sat
7/25
Partly Cloudy
45%
18°
30°
Sun
7/26
Clear
17%
23°
34°
Mon
7/27
Clear
17%
23°
34°
Tue
7/28
Rain
28%
19°
33°
Wed
7/29
Drizzle
44%
18°
29°
Thu
7/30
Drizzle
44%
15°
29°
Fri
7/31
Drizzle
51%
16°
29°
Sat
8/1
Drizzle
60%
18°
29°
Sun
8/2
Drizzle
60%
19°
30°
Mon
8/3
Drizzle
60%
19°
31°
Tue
8/4
Drizzle
60%
20°
31°
43
Good
U.S. Air Quality Index · Dominant: PM2.5
50 100 150 200

Air quality is satisfactory and poses little or no health risk.

Pollutant Breakdown · Today
PM2.5
Fine particulate matter
Dominant
43 AQI 7.8 µg/m³
O3
Ground-level ozone
37 AQI 41 ppb
3-Day Outlook
DayAQICategoryO₃PM2.5
Today 43 Good 37 43
Thu 29 Good 29 16
Fri 35 Good 35 8
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 Tue Jul 21, 23:00'Z' · F0 · 130 (13 km CONUS/NA)
Hodograph · kt
10 20 30 40 50 60 SM
0–1 1–3 3–6 6–9 km
Instability
SBCAPE200 J/kg
MLCAPE186 J/kg
MUCAPE301 J/kg
SBCIN-140 J/kg
MLCIN0 J/kg
Lifted Index-0.1
Kinematics
0–6 km Shear40 kt
0–1 km Shear11 kt
Eff. Shear43 kt
0–1 km SRH-82
0–3 km SRH-104
Eff. SRH-104
Storm Motion278° @ 32 kt
0–1 km EHI-0.1
Composite Parameters
Sig. Tornado0.0
STP (eff)0.0
Supercell0.0
K-Index6.3
Thermo & Levels
PWAT1.52 in
0–3 km LR4.9 °C/km
700–500 LR5.8 °C/km
Total Totals40.5
LCL911 hPa
LFC820 hPa
EL203 hPa
Freezing Lvl17,044 ft