Hourly Weather | Today Monday, April 27, 2026
Active Weather Warnings
O'Fallon, Missouri
9 PM
Stormy Weather
70°
Feels Like 63°
51
Humidity: 80%
UV Index: 0
Wind: 12 mph
10 PM
Cloudy Night
66°
Feels Like 64°
47
Humidity: 84%
UV Index: 0
Wind: 10 mph
11 PM
Cloudy Night
64°
Feels Like 63°
34
Humidity: 87%
UV Index: 0
Wind: 10 mph

Hourly Air Quality Forecast - AQI (US EPA)

9 PM
34 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 2.2 µg/m³
  • PM10: 2.87 µg/m³
  • O3: 0.037 ppm
  • NO2: 0.5 ppb
  • SO2: 0.1 ppb
  • CO: 0.11 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

10 PM
33 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 2.6 µg/m³
  • PM10: 3.17 µg/m³
  • O3: 0.035 ppm
  • NO2: 0.5 ppb
  • SO2: 0.1 ppb
  • CO: 0.12 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

11 PM
30 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 2.79 µg/m³
  • PM10: 3.2 µg/m³
  • O3: 0.032 ppm
  • NO2: 0.5 ppb
  • SO2: 0.2 ppb
  • CO: 0.12 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

Weather Alerts and Warnings for O'Fallon

Extreme Future Possible

Tornado Watch

Tornado Watch issued April 27 at 7:01PM CDT until April 27 at 9:00PM CDT by NWS St Louis MO
Apr 27, 7:01 PM Apr 27, 9:00 PM
TORNADO WATCH 160 REMAINS VALID UNTIL 9 PM CDT THIS EVENING FOR
THE FOLLOWING AREAS

IN ILLINOIS THIS WATCH INCLUDES 12 COUNTIES

IN SOUTH CENTRAL ILLINOIS

BOND CLINTON FAYETTE
MARION MONTGOMERY WASHINGTON

IN SOUTHWEST ILLINOIS

JERSEY MACOUPIN MADISON
MONROE RANDOLPH SAINT CLAIR

IN MISSOURI THIS WATCH INCLUDES 12 COUNTIES

IN EAST CENTRAL MISSOURI

CRAWFORD FRANKLIN JEFFERSON
SAINT CHARLES SAINT LOUIS SAINT LOUIS CITY
WASHINGTON

IN SOUTHEAST MISSOURI

IRON MADISON REYNOLDS
SAINT FRANCOIS SAINTE GENEVIEVE

THIS INCLUDES THE CITIES OF ALTON, BELLEVILLE, CAHOKIA,
CENTRALIA, CHESTER, EDWARDSVILLE, FARMINGTON, LITCHFIELD,
SAINT CHARLES, SAINT LOUIS, SALEM, SPARTA, SULLIVAN, UNION,
VANDALIA, AND WASHINGTON.
Updated: Apr 27, 7:11 PM Source: NWS Alert
Severe Future Possible

Flood Watch

Flood Watch issued April 27 at 11:18AM CDT until April 27 at 9:00PM CDT by NWS St Louis MO
Apr 27, 11:18 AM Apr 27, 9:00 PM
WHAT: Flash flooding caused by excessive rainfall is possible.

WHERE: Portions of Illinois, including the following areas, Bond
IL, Calhoun IL, Clinton IL, Fayette IL, Greene IL, Jersey IL,
Macoupin IL, Madison IL, Marion IL, Monroe IL, Montgomery IL, Saint
Clair IL and Washington IL and Missouri, including the following
areas, Audrain MO, Boone MO, Callaway MO, Cole MO, Franklin MO,
Gasconade MO, Jefferson MO, Lincoln MO, Moniteau MO, Montgomery MO,
Osage MO, Pike MO, Saint Charles MO, Saint Louis City MO, Saint
Louis MO and Warren MO.

WHEN: Until 9 PM CDT this evening.

IMPACTS: Excessive runoff may result in flooding of rivers,
creeks, streams, and other low-lying and flood-prone locations.

ADDITIONAL DETAILS:
- Thunderstorms producing heavy rainfall moving over the same areas
will have the potential to produce flash flooding.
+ Read More
You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued.
Updated: Apr 27, 7:11 PM Source: NWS Alert