Air quality
Air quality in Decatur today
Updated
Good (US AQI 45) Air quality is satisfactory and poses little or no risk; a good time for outdoor activity. Model estimate for Sun, Oct 25, 9:00 pm (02:00 UTC).
Live AQI, PM2.5, PM10 and ozone for Decatur, Illinois, United States, with a 48-hour forecast and the best time to be outside.
- US AQI now
- 45 Good
- PM2.5
- 11 µg/m³ 0.8× WHO 24-h guideline
- PM10
- 11 µg/m³
- Ozone
- 58 µg/m³
- Dominant pollutant
- ozone sub-index 45
- Best hour tomorrow
- 6:00 am AQI 53
- European AQI
- 33
Air quality in Decatur right now
Right now the modelled US Air Quality Index for Decatur, Illinois, United States is 45, which falls in the "Good" band (up to 50). Air quality is satisfactory and poses little or no risk; a good time for outdoor activity.
The index is driven mainly by ozone, whose own sub-index is 45. Ozone usually peaks in the afternoon on sunny days and falls back after sunset.
PM2.5 is 11 µg/m³, within the WHO 24-hour guideline of 15 µg/m³; PM10 is 11 µg/m³ against a guideline of 45; ozone is 58 µg/m³ (below the WHO 8-hour level of 100); nitrogen dioxide is 16 µg/m³ (below the 24-hour guideline of 25).
Also this hour: carbon monoxide 209 µg/m³.
NASA FIRMS shows 68 fire hotspots within 300 km in the last day (nearest about 104 km), but particle levels are not elevated enough to point to smoke right now.
Decatur AQI forecast: next 48 hours
Over the next 24 hours the AQI is forecast to range from 43 around Sun 10:00 pm to 55 around Mon 10:00 am, from "Good" at best to "Moderate" at worst.
The following day looks similar, averaging about 54.
| Local time (America/Chicago) | US AQI | Category | PM2.5 µg/m³ | PM10 µg/m³ | Ozone µg/m³ |
|---|---|---|---|---|---|
| Sun 9:00 pm | 45 | Good | 11.3 | 11 | 58 |
| Mon 12:00 am | 47 | Good | 12 | 12 | 52 |
| Mon 3:00 am | 51 | Moderate | 13.9 | 14 | 51 |
| Mon 6:00 am | 53 | Moderate | 15.5 | 16 | 44 |
| Mon 9:00 am | 54 | Moderate | 14.6 | 15 | 44 |
| Mon 12:00 pm | 55 | Moderate | 6.9 | 7 | 81 |
| Mon 3:00 pm | 55 | Moderate | 5.7 | 6 | 112 |
| Mon 6:00 pm | 54 | Moderate | 6.8 | 7 | 82 |
| Mon 9:00 pm | 53 | Moderate | 9.4 | 10 | 55 |
| Tue 12:00 am | 53 | Moderate | 13.4 | 13 | 41 |
| Tue 3:00 am | 53 | Moderate | 16.5 | 17 | 34 |
| Tue 6:00 am | 54 | Moderate | 17.2 | 17 | 30 |
| Tue 9:00 am | 54 | Moderate | 12.8 | 13 | 45 |
| Tue 12:00 pm | 54 | Moderate | 6 | 7 | 91 |
| Tue 3:00 pm | 54 | Moderate | 5.4 | 6 | 109 |
| Tue 6:00 pm | 54 | Moderate | 6.3 | 7 | 81 |
| Tue 9:00 pm | 53 | Moderate | 8.3 | 8 | 65 |
Every third hour of the CAMS forecast via Open-Meteo. US AQI uses rolling averages (24 h for particles, 8 h for ozone), so it moves more slowly than the hourly concentrations.
Best time to be outside in Decatur tomorrow
Between 6 am and 9 pm local time, the cleanest air tomorrow is forecast around 6:00 am (AQI 53, Moderate) and the worst around 10:00 am (AQI 55). The difference across the day is small, so timing matters little.
Decatur vs the rest of United States
Across 619 United States cities we track, the average US AQI right now is 52 (Moderate). Decatur at 45 is 7 points cleaner than average.
For context, the median across 3,556 cities worldwide is 58.
Air quality in cities near Decatur
| City | Distance | US AQI | Category | PM2.5 µg/m³ |
|---|---|---|---|---|
| Springfield, IL | 59 km | 43 | Good | 6.4 |
| Normal | 75 km | 45 | Good | 5 |
| Charleston, IL | 77 km | 46 | Good | 7.9 |
| Peoria, IL | 109 km | 41 | Good | 7.9 |
| North Peoria | 111 km | 41 | Good | 7.9 |
| St. Louis | 172 km | 42 | Good | 9.7 |
| Saint Charles | 176 km | 48 | Good | 13.7 |
| Chesterfield, MO | 191 km | 48 | Good | 13.7 |
Model vs measured
We found no measured PM2.5 sensor cell within 25 km of Decatur, so the numbers on this page are model estimates. Models capture regional pollution well but can miss very local sources such as a busy road or a nearby fire.
Advice for sensitive groups
With the AQI at 45, there is no need for sensitive groups to change plans. People with asthma should still carry their reliever inhaler as usual.
What the US AQI numbers mean
| US AQI | Category | What it means |
|---|---|---|
| 0-50 | Good | Air quality is satisfactory and poses little or no risk; a good time for outdoor activity. |
| 51-100 | Moderate | Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors. |
| 101-150 | Unhealthy for Sensitive Groups | People with heart or lung disease, older adults, children and teens should cut back on prolonged or heavy exertion outdoors. |
| 151-200 | Unhealthy | Everyone should reduce prolonged or heavy exertion outdoors; sensitive groups should avoid it and keep windows closed. |
| 201-300 | Very Unhealthy | Health alert: everyone should avoid prolonged or heavy exertion outdoors, and sensitive groups should stay indoors. |
| 301-500 | Hazardous | Emergency conditions: everyone should avoid all outdoor physical activity and stay indoors with filtered air if possible. The scale tops out at 500; heavier dust or smoke is shown as 500. |
Values on this page are modelled by CAMS (Copernicus) and served by Open-Meteo; they are estimates for the area around the city centre, not readings from an official monitor.
Nearby cities
More for Decatur
Air quality elsewhere
Data: Open-Meteo Air Quality API, Copernicus Atmosphere Monitoring Service (CAMS), NASA FIRMS.