Billings Air Quality in October
Across 2019–2025, Billings's October air quality had a median AQI of 34 (Good) over 215 monitored days in the Billings, MT area. 0.0% of October days (0 of 215) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 84.7% of days. The cleanest October on record here was 2023 (median AQI 29, 0 days above 100) and the worst was 2022 (median 42, 0 days above 100, peak AQI 63).
- Good: 84.2%
- Moderate: 15.8%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Billings
Today's main pollutant in Billings is ground-level ozone (AQI 21). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
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How is the air in Billings in October?
Good on a typical day: median AQI 34 across 2019–2025, with 0.0% of October days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓84.2% of October days were Good (AQI 0–50), 15.8% Moderate (51–100).
- ✓0 days of 215 reached AQI 101+; the October peak was 82.
- ✓Best October: 2023; worst October: 2022.
Frequently asked questions
What is the air quality like in Billings in October?▾
Across 2019–2025, the median daily AQI in Billings in October was 34 (Good). 84.2% of days were Good, 15.8% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 215 monitored days in EPA's Air Quality System.
Is October a good time for outdoor exercise in Billings?▾
A typical October day in Billings sits in the Good range (median AQI 34), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of October days reached AQI 101+ in 2019–2025.
Which pollutant causes Billings's October air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 84.7% of October days in Billings. The highest October AQI recorded in 2019–2025 was 82 (Moderate), in 2022.
Billings October air quality, year by year
Billings October air quality by year (Billings, MT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 30 | 0 | 59 | PM2.5 |
| 2020 | 31 | 42 | 0 | 72 | PM2.5 |
| 2021 | 31 | 37 | 0 | 75 | PM2.5 |
| 2022worst | 31 | 42 | 0 | 63 | PM2.5 |
| 2023cleanest | 29 | 29 | 0 | 52 | PM2.5 |
| 2024 | 31 | 39 | 0 | 82 | PM2.5 |
| 2025 | 31 | 30 | 0 | 41 | O3 |
What October air means in Billings
A typical October day in Billings sits in the Good range (median AQI 34), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of October days reached AQI 101+ in 2019–2025.
October's median AQI of 34 is below Billings's whole-year median of 38, making it one of the area's cleaner periods. Nationally, the median October AQI across every EPA metro area (102,872 metro-days, 2019–2025) is 38, so Billings runs below the national October norm; 0.0% of its October days topped AQI 100 versus 1.3% nationally (below average).
October is part of Billings's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Billings
The latest EPA AirNow observation puts Billings's AQI at 21 (O3). The figures above are multi-year month 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.