Billings Air Quality in December
Across 2019–2025, Billings's December air quality had a median AQI of 32 (Good) over 215 monitored days in the Billings, MT area. 0.0% of December days (0 of 215) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 87.4% of days. The cleanest December on record here was 2023 (median AQI 28, 0 days above 100) and the worst was 2022 (median 37, 0 days above 100, peak AQI 74).
- Good: 82.8%
- Moderate: 17.2%
- 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.
Recommended: Levoit Core 300 — True HEPA + activated carbon · CADR ~141 CFM · rooms up to 219 sq ft
As an Amazon Associate, we earn from qualifying purchases.
How is the air in Billings in December?
Good on a typical day: median AQI 32 across 2019–2025, with 0.0% of December days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓82.8% of December days were Good (AQI 0–50), 17.2% Moderate (51–100).
- ✓0 days of 215 reached AQI 101+; the December peak was 74.
- ✓Best December: 2023; worst December: 2022.
Frequently asked questions
What is the air quality like in Billings in December?▾
Across 2019–2025, the median daily AQI in Billings in December was 32 (Good). 82.8% of days were Good, 17.2% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 215 monitored days in EPA's Air Quality System.
Is December a good time for outdoor exercise in Billings?▾
A typical December day in Billings sits in the Good range (median AQI 32), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of December days reached AQI 101+ in 2019–2025.
Which pollutant causes Billings's December air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 87.4% of December days in Billings. The highest December AQI recorded in 2019–2025 was 74 (Moderate), in 2022.
Billings December air quality, year by year
Billings December air quality by year (Billings, MT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 31 | 0 | 69 | PM2.5 |
| 2020 | 29 | 32 | 0 | 62 | PM2.5 |
| 2021 | 31 | 34 | 0 | 64 | PM2.5 |
| 2022worst | 31 | 37 | 0 | 74 | PM2.5 |
| 2023cleanest | 31 | 28 | 0 | 51 | PM2.5 |
| 2024 | 31 | 35 | 0 | 70 | PM2.5 |
| 2025 | 31 | 32 | 0 | 59 | PM2.5 |
What December air means in Billings
A typical December day in Billings sits in the Good range (median AQI 32), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of December days reached AQI 101+ in 2019–2025.
December's median AQI of 32 is below Billings's whole-year median of 38, making it one of the area's cleaner periods. Nationally, the median December AQI across every EPA metro area (95,590 metro-days, 2019–2025) is 39, so Billings runs below the national December norm; 0.0% of its December days topped AQI 100 versus 0.7% nationally (about the same).
December is part of Billings's winter season (December, January, February); the winter 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.