Hourly Weather | Today Wednesday, August 12, 2026
Active Weather Warnings
St. Charles, Missouri
8 AM
Cloudy Weather
81°
Feels Like 84°
7
Humidity: 75%
UV Index: 2
Wind: 9 mph
9 AM
Cloudy Weather
82°
Feels Like 90°
7
Humidity: 73%
UV Index: 3
Wind: 9 mph
10 AM
Cloudy Weather
84°
Feels Like 95°
6
Humidity: 70%
UV Index: 4
Wind: 10 mph
11 AM
Cloudy Weather
88°
Feels Like 99°
5
Humidity: 62%
UV Index: 6
Wind: 10 mph
12 PM
Cloudy Weather
90°
Feels Like 102°
5
Humidity: 58%
UV Index: 8
Wind: 10 mph
1 PM
Cloudy Weather
91°
Feels Like 104°
8
Humidity: 56%
UV Index: 9
Wind: 9 mph
2 PM
Sunny with a Chance of Thunderstorms
88°
Feels Like 100°
51
Humidity: 73%
UV Index: 8
Wind: 10 mph
3 PM
Cloudy Weather
91°
Feels Like 100°
47
Humidity: 56%
UV Index: 6
Wind: 10 mph
4 PM
Cloudy Weather
95°
Feels Like 102°
36
Humidity: 49%
UV Index: 4
Wind: 9 mph
5 PM
Cloudy Weather
93°
Feels Like 100°
20
Humidity: 51%
UV Index: 3
Wind: 9 mph
6 PM
Cloudy Weather
91°
Feels Like 99°
20
Humidity: 55%
UV Index: 2
Wind: 9 mph
7 PM
Cloudy Weather
90°
Feels Like 97°
24
Humidity: 62%
UV Index: 1
Wind: 9 mph
8 PM
Cloudy Weather
86°
Feels Like 93°
34
Humidity: 69%
UV Index: 0
Wind: 8 mph
9 PM
Cloudy Night
84°
Feels Like 91°
34
Humidity: 73%
UV Index: 0
Wind: 8 mph
10 PM
Cloudy Night
82°
Feels Like 90°
38
Humidity: 78%
UV Index: 0
Wind: 7 mph
11 PM
Cloudy Night
81°
Feels Like 88°
49
Humidity: 80%
UV Index: 0
Wind: 8 mph

Hourly Air Quality Forecast - AQI (US EPA)

8 AM
21 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 3.33 µg/m³
  • PM10: 3.85 µg/m³
  • O3: 0.023 ppm
  • NO2: 0.6 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

9 AM
21 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 3.2 µg/m³
  • PM10: 3.77 µg/m³
  • O3: 0.022 ppm
  • NO2: 0.6 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

10 AM
22 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 3.08 µg/m³
  • PM10: 3.69 µg/m³
  • O3: 0.024 ppm
  • NO2: 0.5 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

11 AM
26 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 2.85 µg/m³
  • PM10: 3.52 µg/m³
  • O3: 0.028 ppm
  • NO2: 0.3 ppb
  • SO2: 0.2 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

12 PM
28 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 2.77 µg/m³
  • PM10: 3.47 µg/m³
  • O3: 0.030 ppm
  • NO2: 0.3 ppb
  • SO2: 0.2 ppb
  • CO: 0.08 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 2.74 µg/m³
  • PM10: 3.46 µg/m³
  • O3: 0.032 ppm
  • NO2: 0.2 ppb
  • SO2: 0.2 ppb
  • CO: 0.08 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 2.55 µg/m³
  • PM10: 3.21 µg/m³
  • O3: 0.036 ppm
  • NO2: 0.2 ppb
  • SO2: 0.2 ppb
  • CO: 0.08 ppm

Health Recommendations:

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

3 PM
35 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 2.54 µg/m³
  • PM10: 3.09 µg/m³
  • O3: 0.038 ppm
  • NO2: 0.2 ppb
  • SO2: 0.1 ppb
  • CO: 0.08 ppm

Health Recommendations:

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

4 PM
36 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 2.58 µg/m³
  • PM10: 3.08 µg/m³
  • O3: 0.039 ppm
  • NO2: 0.2 ppb
  • SO2: 0.1 ppb
  • CO: 0.08 ppm

Health Recommendations:

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

5 PM
36 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 2.54 µg/m³
  • PM10: 3.01 µg/m³
  • O3: 0.038 ppm
  • NO2: 0.3 ppb
  • SO2: 0.1 ppb
  • CO: 0.08 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 2.45 µg/m³
  • PM10: 2.92 µg/m³
  • O3: 0.037 ppm
  • NO2: 0.4 ppb
  • SO2: 0.1 ppb
  • CO: 0.08 ppm

Health Recommendations:

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

7 PM
32 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 2.35 µg/m³
  • PM10: 2.81 µg/m³
  • O3: 0.034 ppm
  • NO2: 0.5 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 2.27 µg/m³
  • PM10: 2.72 µg/m³
  • O3: 0.032 ppm
  • NO2: 0.6 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 2.26 µg/m³
  • PM10: 2.71 µg/m³
  • O3: 0.030 ppm
  • NO2: 0.6 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 2.3 µg/m³
  • PM10: 2.75 µg/m³
  • O3: 0.028 ppm
  • NO2: 0.6 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 2.3 µg/m³
  • PM10: 2.74 µg/m³
  • O3: 0.026 ppm
  • NO2: 0.6 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

Weather Alerts and Warnings for St. Charles

Severe Future Likely

Extreme Heat Watch

Extreme Heat Watch issued August 8 at 2:33PM CDT until August 12 at 8:00PM CDT by NWS St Louis MO
Aug 9, 12:00 PM Aug 12, 8:00 PM
WHAT: Dangerously hot conditions with heat index values up to 109
possible.

WHERE: Portions of south central and southwest Illinois and
central and east central Missouri.

WHEN: From Sunday afternoon through Wednesday evening.

IMPACTS: Heat related illnesses increase significantly during
extreme heat and high humidity events.
+ Read More
Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.
Updated: Aug 9, 12:55 AM Source: NWS Alert
Severe Expected Likely

Extreme Heat Warning

Extreme Heat Warning issued August 12 at 1:45AM CDT until August 13 at 8:00PM CDT by NWS St Louis MO
Aug 12, 1:45 AM Aug 13, 8:00 PM
WHAT: Dangerously hot conditions with heat index values up to 111.

WHERE: Portions of south central and southwest Illinois and
central and east central Missouri.

WHEN: Until 8 PM CDT Thursday.

IMPACTS: Heat related illnesses increase significantly during
extreme heat and high humidity events.
+ Read More
Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Young children and pets should never be left unattended in vehicles under any circumstances. Take extra precautions if you work or spend time outside. When possible reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear lightweight and loose fitting clothing when possible. To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency! Call 9 1 1. People in the Saint Louis Metropolitan Area can get information about cooling centers or energy assistance related to the excessive heat by calling the United Way of Greater Saint Louis at 800-427-4626, or if calling from a land line phone dial 2-1-1. You can also call Cool Down Saint Louis at 314-241-7668.
Updated: Aug 12, 7:26 AM Source: NWS Alert