Portland, ME Air Quality in 2024
In 2024, Portland's air quality (Portland-South Portland, ME area) had a median daily AQI of 39 (Good) across 366 monitored days. 1 day (0.3%) reached Unhealthy for Sensitive Groups or worse, 289 were Good, and the year's peak AQI was 129 (Unhealthy for Sensitive Groups). Ground-level ozone set the daily AQI on 243 of those days. The cleanest month of 2024 was October (median AQI 31, 0 days above 100) and the worst was June (median 43, 1 day above 100, peak 129).
- Good: 79.0%
- Moderate: 20.8%
- Unhealthy for Sensitive Groups: 0.3%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Portland
Today's main pollutant in Portland is ground-level ozone (AQI 29). 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
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How was Portland's air quality in 2024?
Good on a typical day: median AQI 39, with 1 day above AQI 100 out of 366 monitored — the 2nd cleanest of 7 years on record for the area.
- ✓Peak AQI in 2024: 129 (Unhealthy for Sensitive Groups).
- ✓Ground-level ozone was the main pollutant on 243 days.
- ✓Cleanest month: October; worst: June.
Frequently asked questions
What was the average AQI in Portland in 2024?▾
EPA's Air Quality System puts Portland's (Portland-South Portland, ME) median daily AQI for 2024 at 39, which is Good. 1 day were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 129.
Which month had the worst air quality in Portland in 2024?▾
The cleanest month of 2024 was October (median AQI 31, 0 days above 100) and the worst was June (median 43, 1 day above 100, peak 129).
Was 2024 a good or bad year for Portland's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2024 ranks 2nd cleanest by days above AQI 100. 2024's median of 39 is in line with the area's typical annual median of 40.
Portland month by month in 2024
Portland air quality month by month, 2024 (Portland-South Portland, ME, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 38 | 0 | 79 | O3 |
| February | 29 | 41 | 0 | 66 | O3 |
| March | 31 | 40 | 0 | 45 | O3 |
| April | 30 | 42 | 0 | 58 | O3 |
| May | 31 | 37 | 0 | 74 | O3 |
| Juneworst | 30 | 43 | 1 | 129 | O3 |
| July | 31 | 53 | 0 | 97 | PM2.5 |
| August | 31 | 50 | 0 | 74 | PM2.5 |
| September | 30 | 34 | 0 | 52 | O3 |
| Octobercleanest | 31 | 31 | 0 | 60 | O3 |
| November | 30 | 32 | 0 | 44 | O3 |
| December | 31 | 35 | 0 | 73 | O3 |
How 2024 compares
Among the 7 years EPA has published for the area (2019–2025), 2024 ranks 2nd cleanest by days above AQI 100.
2024's median of 39 is in line with the area's typical annual median of 40.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Portland
The latest EPA AirNow observation puts Portland's AQI at 29 (O3). The figures above are multi-year annual statistics, not today's reading.
View current Portland air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Portland-South Portland, ME), 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.