Portland, ME Air Quality in 2020
In 2020, Portland's air quality (Portland-South Portland, ME area) had a median daily AQI of 42 (Good) across 366 monitored days. 0 days (0.0%) reached Unhealthy for Sensitive Groups or worse, 262 were Good, and the year's peak AQI was 97 (Moderate). Fine particulate matter (PM2.5) set the daily AQI on 196 of those days. The cleanest month of 2020 was October (median AQI 30, 0 days above 100) and the worst was June (median 53, 0 days above 100, peak 77).
- Good: 71.6%
- Moderate: 28.4%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Portland
Today's main pollutant in Portland is ground-level ozone (AQI 27). 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 was Portland's air quality in 2020?
Good on a typical day: median AQI 42, with 0 days above AQI 100 out of 366 monitored — the 1st cleanest of 7 years on record for the area.
- ✓Peak AQI in 2020: 97 (Moderate).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 196 days.
- ✓Cleanest month: October; worst: June.
Frequently asked questions
What was the average AQI in Portland in 2020?▾
EPA's Air Quality System puts Portland's (Portland-South Portland, ME) median daily AQI for 2020 at 42, which is Good. 0 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 97.
Which month had the worst air quality in Portland in 2020?▾
The cleanest month of 2020 was October (median AQI 30, 0 days above 100) and the worst was June (median 53, 0 days above 100, peak 77).
Was 2020 a good or bad year for Portland's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2020 ranks 1st cleanest by days above AQI 100 — the best year on record here. 2020's median of 42 is in line with the area's typical annual median of 40.
Portland month by month in 2020
Portland air quality month by month, 2020 (Portland-South Portland, ME, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 48 | 0 | 73 | PM2.5 |
| February | 29 | 52 | 0 | 68 | PM2.5 |
| March | 31 | 43 | 0 | 61 | O3 |
| April | 30 | 44 | 0 | 57 | O3 |
| May | 31 | 43 | 0 | 61 | O3 |
| Juneworst | 30 | 53 | 0 | 77 | PM2.5 |
| July | 31 | 48 | 0 | 87 | PM2.5 |
| August | 31 | 39 | 0 | 87 | O3 |
| September | 30 | 31 | 0 | 54 | O3 |
| Octobercleanest | 31 | 30 | 0 | 49 | O3 |
| November | 30 | 33 | 0 | 97 | PM2.5 |
| December | 31 | 36 | 0 | 67 | PM2.5 |
How 2020 compares
Among the 7 years EPA has published for the area (2019–2025), 2020 ranks 1st cleanest by days above AQI 100 — the best year on record here.
2020's median of 42 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 27 (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.