Excessive 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

Johnson County, Illinois, United States

Last updated: 2:25 AM CDT  ·  Refresh
25°C
Feels like 29°
Clear
▲ 38°  /  ▼ 23°
Wind
2 mph S
Humidity
80%
Dew Point
22°
Pressure
29.47 inHg
Visibility
10 mi
UV Index
0.0
Cloud Cover
0%
Sunrise
6:28 AM
Sunset
7:19 PM
Drag to pan · double-click to forecast a point
WeatherAI™ Analysis

WeatherAI Analysis: Johnson County is currently clear at 25°C. Dry conditions are expected through the next 24 hours. Atmospheric instability is elevated (CAPE up to 2282 J/kg) — isolated convective development possible. Sunrise: 6:28AM · Sunset: 7:19PM.

Alerts

Excessive 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
52 AQI · Moderate Dominant: PM2.5 Air Quality
Hourly Forecast · Next 24 Hours
Now
25°
10%
3 AM
24°
9%
4 AM
24°
9%
5 AM
23°
9%
6 AM
23°
9%
7 AM
24°
16%
8 AM
26°
16%
9 AM
30°
17%
10 AM
32°
15%
11 AM
33°
15%
12 PM
34°
16%
1 PM
36°
16%
2 PM
37°
18%
3 PM
37°
19%
4 PM
36°
19%
5 PM
37°
19%
6 PM
36°
14%
7 PM
34°
9%
8 PM
33°
9%
9 PM
28°
9%
10 PM
27°
9%
11 PM
27°
9%
12 AM
27°
9%
1 AM
27°
9%
7-Day Forecast
Today
38° 23°
Mostly Clear.
Sat
39° 23°
Partly Cloudy with a 34% chance of rain.
Sun
37° 18°
Clear.
Mon
34° 13°
Mostly Clear.
Tue
38° 18°
Clear.
Wed
41° 22°
Clear with a 28% chance of rain.
Thu
39° 19°
Rain, 28% chance.
TimeTempConditionsPrecipWindHumidity
Now 25° Clear 10% 2 mph S 80%
3 AM 24° Clear 9% 3 mph WSW 79%
4 AM 24° Clear 9% 3 mph SW 79%
5 AM 23° Clear 9% 3 mph S 80%
6 AM 23° Clear 9% 3 mph S 82%
7 AM 24° Clear 16% 3 mph S 80%
8 AM 26° Clear 16% 3 mph SSW 71%
9 AM 30° Clear 17% 4 mph SSW 62%
10 AM 32° Clear 15% 4 mph SW 54%
11 AM 33° Clear 15% 3 mph SW 49%
12 PM 34° Mostly Clear 16% 3 mph SW 45%
1 PM 36° Mostly Clear 16% 3 mph SW 42%
2 PM 37° Mostly Clear 18% 4 mph SSW 42%
3 PM 37° Mostly Clear 19% 5 mph S 41%
4 PM 36° Mostly Clear 19% 6 mph S 42%
5 PM 37° Mostly Clear 19% 5 mph S 46%
6 PM 36° Clear 14% 4 mph S 50%
7 PM 34° Clear 9% 4 mph S 55%
8 PM 33° Clear 9% 4 mph S 59%
9 PM 28° Clear 9% 4 mph S 63%
10 PM 27° Clear 9% 3 mph S 66%
11 PM 27° Clear 9% 3 mph S 68%
12 AM 27° Clear 9% 4 mph SSW 70%
1 AM 27° Clear 9% 4 mph SSW 72%
15-Day Forecast
Today
9/4
Mostly Clear
19%
23°
38°
Sat
9/5
Partly Cloudy
34%
23°
39°
Sun
9/6
Clear
17%
18°
37°
Mon
9/7
Mostly Clear
7%
13°
34°
Tue
9/8
Clear
3%
18°
38°
Wed
9/9
Clear
28%
22°
41°
Thu
9/10
Rain
28%
19°
39°
Fri
9/11
Rain
44%
16°
38°
Sat
9/12
Clear
44%
21°
43°
Sun
9/13
Clear
44%
18°
37°
Mon
9/14
Clear
60%
21°
38°
Tue
9/15
Drizzle
60%
22°
38°
Wed
9/16
Drizzle
60%
21°
38°
Thu
9/17
Drizzle
60%
19°
35°
Fri
9/18
Clear
25%
19°
34°
52
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
52 AQI 9.9 µg/m³
O3
Ground-level ozone
48 AQI 52 ppb
3-Day Outlook
DayAQICategoryO₃PM2.5
Today 52 Moderate 48 52
Sat 57 Moderate 44 57
Sun 53 Moderate 44 53
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
SBCAPE387 J/kg
MLCAPE927 J/kg
MUCAPE1365 J/kg
SBCIN-416 J/kg
MLCIN-163 J/kg
Lifted Index-1.3
Kinematics
0–6 km Shear3 kt
0–1 km Shear13 kt
Eff. Shear3 kt
0–1 km SRH30
0–3 km SRH14
Eff. SRH-5
Storm Motion307° @ 11 kt
0–1 km EHI0.1
Composite Parameters
Sig. Tornado0.0
STP (eff)0.0
Supercell0.0
K-Index34.9
Thermo & Levels
PWAT1.70 in
0–3 km LR4.9 °C/km
700–500 LR5.5 °C/km
Total Totals46.3
LCL953 hPa
LFC595 hPa
EL264 hPa
Freezing Lvl16,260 ft