Today | Weather | Monday, June 29, 2026

Active Weather Warnings

Weather in St. Charles, Missouri

08:01 PM

Now

88° F

Feels Like 91°

Precipitation 0 %

Wind 9 mph

UV Index (0 - 11+) 0

Humidity 61 %

Today

Day 99°

Night 75°

Precipitation 1 %

Wind 12 mph

UV Index (0 - 11+) 11

Warning: Extreme UV Index Today: 11

Overexposure to the sun's harmful UV rays can cause sunburn and increase the risk of developing skin cancer, including melanoma. Protect yourself by wearing clothing that covers your skin, sunglasses, and a hat. Apply a broad-spectrum sunscreen with an SPF of 30 or higher every two hours, even on cloudy days. Minimize direct sun exposure during peak hours (10 AM to 4 PM) to reduce the risk.

St. Charles Weather Forecast Updated

Last updated on June 29, 2026 at 6:42 PM

Air Quality in St. Charles

NOW

21 AQI

Good air quality Dominant pollutant: O₃

Pollutant Concentrations:

PM_2.5 2.55 µg/m³

PM₁₀ 4 µg/m³

O₃ 0.023 ppm

NO₂ 0.3 ppb

SO₂ 0.1 ppb

CO 0.09 ppm

NH₃ 0.67 µg/m³

NO 0.03 µg/m³

PM_2.5 – Fine particles <2.5μm

PM₁₀ – Inhalable particles <10μm

O₃ – Ozone

NO₂ – Nitrogen dioxide

SO₂ – Sulfur dioxide

CO – Carbon monoxide

NH₃ – Ammonia

NO – Nitric oxide

Health Recommendations:

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

Show raw pollutant concentrations (µg/m³)

PM_2.5 – 2.55 µg/m³

PM₁₀ – 4 µg/m³

O₃ – 45.56 µg/m³

NO₂ – 0.59 µg/m³

SO₂ – 0.16 µg/m³

CO – 101.49 µg/m³

NH₃ – 0.67 µg/m³

NO – 0.03 µg/m³

View Hourly Air Quality Forecast

Weather Alerts and Warnings for St. Charles

Severe Future Likely

Extreme Heat Watch

Extreme Heat Watch issued June 27 at 1:59AM CDT until July 3 at 12:00AM CDT by NWS St Louis MO

Jun 28, 12:00 PM → Jul 3, 12:00 AM

WHAT: Dangerously hot conditions with heat index values of 105 to
110 possible.

WHERE: In Illinois, Madison IL, Monroe IL, and Saint Clair IL
Counties. In Missouri, Jefferson MO, Saint Charles MO, Saint Louis
City MO, and Saint Louis MO Counties.

WHEN: From Sunday afternoon through Thursday 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: Jun 27, 1:16 PM Source: NWS Alert

Severe Expected Likely

Extreme Heat Warning

Extreme Heat Warning issued June 29 at 2:02PM CDT until July 3 at 10:00PM CDT by NWS St Louis MO

Jun 29, 2:02 PM → Jul 3, 10:00 PM

WHAT: Dangerously hot conditions with heat index values up to 110.

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

WHEN: Until 10 PM CDT Friday.

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.

Updated: Jun 29, 6:42 PM Source: NWS Alert

Weather in St. Charles, Missouri

Warning: Extreme UV Index Today: 11

St. Charles Weather Forecast Updated

Air Quality in St. Charles

Pollutant Concentrations:

Health Recommendations:

Weather Alerts and Warnings for St. Charles

Extreme Heat Watch

Extreme Heat Warning

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