Billings Air Quality in Winter
Across 2019–2025, Billings's winter (December–February) air quality had a median AQI of 31 (Good) over 612 monitored days in the Billings, MT area. 0.0% of winter days (0 of 612) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 86.3% of days. The cleanest winter on record here was 2023 (median AQI 26, 0 days above 100) and the worst was 2025 (median 34, 0 days above 100, peak AQI 77).
- Good: 84.8%
- Moderate: 15.2%
- 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 winter?
Good on a typical day: median AQI 31 across 2019–2025, with 0.0% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓84.8% of winter days were Good (AQI 0–50), 15.2% Moderate (51–100).
- ✓0 days of 612 reached AQI 101+; the winter peak was 77.
- ✓Cleanest month: February; worst month: December.
Frequently asked questions
What is the air quality like in Billings in winter?▾
Across 2019–2025, the median daily AQI in Billings in winter was 31 (Good). 84.8% of days were Good, 15.2% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 612 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in Billings?▾
A typical winter day in Billings sits in the Good range (median AQI 31), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Which pollutant causes Billings's winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 86.3% of winter days in Billings. The highest winter AQI recorded in 2019–2025 was 77 (Moderate), in 2025.
Billings winter air quality, year by year
Billings winter air quality by year (Billings, MT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 72 | 32 | 0 | 69 | PM2.5 |
| 2020 | 89 | 29 | 0 | 70 | PM2.5 |
| 2021 | 90 | 30 | 0 | 71 | PM2.5 |
| 2022 | 90 | 31 | 0 | 74 | PM2.5 |
| 2023cleanest | 90 | 26 | 0 | 55 | PM2.5 |
| 2024 | 91 | 34 | 0 | 70 | O3 |
| 2025worst | 90 | 34 | 0 | 77 | PM2.5 |
What winter air means in Billings
A typical winter day in Billings sits in the Good range (median AQI 31), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Winter's median AQI of 31 is below Billings's whole-year median of 38, making it one of the area's cleaner periods. Nationally, the median Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so Billings runs below the national Winter norm; 0.0% of its Winter days topped AQI 100 versus 0.6% nationally (about the same).
Within the season, February is the cleanest month (median AQI 30, 0.0% of days above 100) and December the worst (median 32, 0.0% above 100).
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 season 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.