Billings Air Quality in May
Across 2019–2025, Billings's May air quality had a median AQI of 26 (Good) over 193 monitored days in the Billings, MT area. 0.0% of May days (0 of 193) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 72.5% of days. The cleanest May on record here was 2022 (median AQI 16, 0 days above 100) and the worst was 2025 (median 43, 0 days above 100, peak AQI 84).
- Good: 93.8%
- Moderate: 6.2%
- 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 May?
Good on a typical day: median AQI 26 across 2019–2025, with 0.0% of May days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓93.8% of May days were Good (AQI 0–50), 6.2% Moderate (51–100).
- ✓0 days of 193 reached AQI 101+; the May peak was 95.
- ✓Best May: 2022; worst May: 2025.
Frequently asked questions
What is the air quality like in Billings in May?▾
Across 2019–2025, the median daily AQI in Billings in May was 26 (Good). 93.8% of days were Good, 6.2% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 193 monitored days in EPA's Air Quality System.
Is May a good time for outdoor exercise in Billings?▾
A typical May day in Billings sits in the Good range (median AQI 26), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of May days reached AQI 101+ in 2019–2025.
Which pollutant causes Billings's May air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 72.5% of May days in Billings. The highest May AQI recorded in 2019–2025 was 95 (Moderate), in 2025.
Billings May air quality, year by year
Billings May air quality by year (Billings, MT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 27 | 0 | 70 | PM2.5 |
| 2020 | 31 | 21 | 0 | 39 | PM2.5 |
| 2021 | 14 | 20 | 0 | 37 | PM2.5 |
| 2022cleanest | 31 | 16 | 0 | 33 | PM2.5 |
| 2023 | 31 | 24 | 0 | 95 | PM2.5 |
| 2024 | 24 | 40 | 0 | 49 | O3 |
| 2025worst | 31 | 43 | 0 | 84 | O3 |
What May air means in Billings
A typical May day in Billings sits in the Good range (median AQI 26), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of May days reached AQI 101+ in 2019–2025.
May's median AQI of 26 is below Billings's whole-year median of 38, making it one of the area's cleaner periods. Nationally, the median May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Billings runs below the national May norm; 0.0% of its May days topped AQI 100 versus 1.3% nationally (below average).
May is part of Billings's spring season (March, April, May); the spring 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.