Portland, ME Air Quality in August
Across 2019–2025, Portland's August air quality had a median AQI of 43 (Good) over 217 monitored days in the Portland-South Portland, ME area. 1.9% of August days (4 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 50.2% of days. The cleanest August on record here was 2022 (median AQI 36, 0 days above 100) and the worst was 2025 (median 42, 3 days above 100, peak AQI 169).
- Good: 65.9%
- Moderate: 32.3%
- Unhealthy for Sensitive Groups: 1.4%
- Unhealthy or worse: 0.5%
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 is the air in Portland in August?
Good on a typical day: median AQI 43 across 2019–2025, with 1.9% of August days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓65.9% of August days were Good (AQI 0–50), 32.3% Moderate (51–100).
- ✓4 days of 217 reached AQI 101+; the August peak was 169.
- ✓Best August: 2022; worst August: 2025.
Frequently asked questions
What is the air quality like in Portland in August?▾
Across 2019–2025, the median daily AQI in Portland in August was 43 (Good). 65.9% of days were Good, 32.3% Moderate, and 1.9% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is August a good time for outdoor exercise in Portland?▾
A typical August day in Portland sits in the Good range (median AQI 43), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 53 of August days (1.9%) reached AQI 101+ in 2019–2025.
Which pollutant causes Portland's August air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 50.2% of August days in Portland. The highest August AQI recorded in 2019–2025 was 169 (Unhealthy), in 2025.
Portland August air quality, year by year
Portland August air quality by year (Portland-South Portland, ME, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 51 | 0 | 64 | PM2.5 |
| 2020 | 31 | 39 | 0 | 87 | O3 |
| 2021 | 31 | 40 | 1 | 129 | O3 |
| 2022cleanest | 31 | 36 | 0 | 80 | O3 |
| 2023 | 31 | 39 | 0 | 82 | PM2.5 |
| 2024 | 31 | 50 | 0 | 74 | PM2.5 |
| 2025worst | 31 | 42 | 3 | 169 | O3 |
What August air means in Portland
A typical August day in Portland sits in the Good range (median AQI 43), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 53 of August days (1.9%) reached AQI 101+ in 2019–2025.
August's median AQI of 43 is in line with Portland's whole-year median of 40, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median August AQI across every EPA metro area (104,152 metro-days, 2019–2025) is 45, so Portland runs in line with the national August norm; 1.9% of its August days topped AQI 100 versus 3.5% nationally (below average).
August is part of Portland's summer season (June, July, August); the summer page pools all three months.
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 month 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.