Today | Weather | Monday, September 21, 2026

Weather in St. Peters, Missouri

12:54 PM
Now
Cloudy Weather
73° F
Feels Like 75°
Precipitation 16 %
Wind 7 mph
UV Index (0 - 11+) 1
Humidity 78 %
Today
Cloudy Weather
Day 73°
Night 64°
Precipitation 25 %
Wind 7 mph
UV Index (0 - 11+) 1

St. Peters Weather Forecast Updated

27 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (September 21, 2025)

Day

88°

Night

63°

Air Quality in St. Peters

NOW
26 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 4.33 µg/m³
PM10 4.39 µg/m³
O3 0.029 ppm
NO2 0.6 ppb
SO2 0.1 ppb
CO 0.12 ppm
NH3 0.22 µg/m³
NO 0.15 µg/m³
PM2.5 – 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)
PM2.54.33 µg/m³
PM104.39 µg/m³
O356.05 µg/m³
NO21.17 µg/m³
SO20.3 µg/m³
CO134.91 µg/m³
NH30.22 µg/m³
NO0.15 µg/m³