Billings Air Quality in 2021
In 2021, Billings's air quality (Billings, MT area) had a median daily AQI of 40 (Good) across 340 monitored days. 10 days (2.9%) reached Unhealthy for Sensitive Groups or worse, 212 were Good, and the year's peak AQI was 167 (Unhealthy). Fine particulate matter (PM2.5) set the daily AQI on 340 of those days. The cleanest month of 2021 was May (median AQI 20, 0 days above 100) and the worst was August (median 62, 5 days above 100, peak 167).
- Good: 62.4%
- Moderate: 34.7%
- Unhealthy for Sensitive Groups: 2.6%
- Unhealthy or worse: 0.3%
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How was Billings's air quality in 2021?
Good on a typical day: median AQI 40, with 10 days above AQI 100 out of 340 monitored — the 6th cleanest of 6 years on record for the area.
- ✓Peak AQI in 2021: 167 (Unhealthy).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 340 days.
- ✓Cleanest month: May; worst: August.
Frequently asked questions
What was the average AQI in Billings in 2021?▾
EPA's Air Quality System puts Billings's (Billings, MT) median daily AQI for 2021 at 40, which is Good. 10 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 167.
Which month had the worst air quality in Billings in 2021?▾
The cleanest month of 2021 was May (median AQI 20, 0 days above 100) and the worst was August (median 62, 5 days above 100, peak 167).
Was 2021 a good or bad year for Billings's air?▾
Among the 6 years EPA has published for the area (2020–2025), 2021 ranks 6th cleanest by days above AQI 100 — the worst year on record here. 2021's median of 40 is in line with the area's typical annual median of 38.
Billings month by month in 2021
Billings air quality month by month, 2021 (Billings, MT, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 28 | 0 | 71 | PM2.5 |
| February | 28 | 32 | 0 | 67 | PM2.5 |
| March | 30 | 28 | 0 | 47 | PM2.5 |
| April | 26 | 29 | 0 | 48 | PM2.5 |
| Maycleanest | 14 | 20 | 0 | 37 | PM2.5 |
| June | 29 | 53 | 0 | 64 | PM2.5 |
| July | 31 | 69 | 4 | 128 | PM2.5 |
| Augustworst | 31 | 62 | 5 | 167 | PM2.5 |
| September | 30 | 53 | 1 | 126 | PM2.5 |
| October | 31 | 37 | 0 | 75 | PM2.5 |
| November | 28 | 33 | 0 | 52 | PM2.5 |
| December | 31 | 34 | 0 | 64 | PM2.5 |
How 2021 compares
Among the 6 years EPA has published for the area (2020–2025), 2021 ranks 6th cleanest by days above AQI 100 — the worst year on record here.
2021's median of 40 is in line with the area's typical annual median of 38.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Billings
The latest EPA AirNow observation puts Billings's AQI at 25 (PM2.5). The figures above are multi-year annual statistics, not today's reading.
View current Billings air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Billings, MT), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.