Today | Weather | Monday, September 21, 2026

Weather in Decatur, Illinois

01:56 PM
Now
Cloudy Weather
68° F
Feels Like 66°
Precipitation 34 %
Wind 9 mph
UV Index (0 - 11+) 2
Humidity 74 %
Today
Rainy Weather
Day 68°
Night 59°
Precipitation 55 %
Wind 10 mph
UV Index (0 - 11+) 2

Decatur Weather Forecast Updated

Last updated on
Weather Forecast History
Last Year's Weather on This Day (September 21, 2025)
Sunny with a Chance of Thunderstorms

Day

84°

Night

66°

Wind

7 mph

UV Index

50

Precipitation

95 %

Air Quality in Decatur

NOW
25 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 2.79 µg/m³
PM10 2.94 µg/m³
O3 0.026 ppm
NO2 2.2 ppb
SO2 0.8 ppb
CO 0.17 ppm
NH3 0.29 µg/m³
NO 0.6 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)
PM2.52.79 µg/m³
PM102.94 µg/m³
O352 µg/m³
NO24.17 µg/m³
SO22.04 µg/m³
CO191.33 µg/m³
NH30.29 µg/m³
NO0.6 µg/m³