Portland, OR Air Quality in August
Across 2019–2025, Portland's August air quality had a median AQI of 42 (Good) over 217 monitored days in the Portland-Vancouver-Hillsboro, OR-WA area. 6.0% of August days (13 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 67.3% of days. The cleanest August on record here was 2020 (median AQI 37, 1 day above 100) and the worst was 2023 (median 50, 5 days above 100, peak AQI 153).
- Good: 69.1%
- Moderate: 24.9%
- Unhealthy for Sensitive Groups: 4.6%
- Unhealthy or worse: 1.4%
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How is the air in Portland in August?
Good on a typical day: median AQI 42 across 2019–2025, with 6.0% of August days above AQI 100. Ground-level ozone is the main driver.
- ✓69.1% of August days were Good (AQI 0–50), 24.9% Moderate (51–100).
- ✓13 days of 217 reached AQI 101+; the August peak was 161.
- ✓Best August: 2020; worst August: 2023.
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 42 (Good). 69.1% of days were Good, 24.9% Moderate, and 6.0% 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 42), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 17 of August days (6.0%) reached AQI 101+ in 2019–2025.
Which pollutant causes Portland's August air quality problems?▾
Ground-level ozone set the daily AQI on 67.3% of August days in Portland. The highest August AQI recorded in 2019–2025 was 161 (Unhealthy), in 2023.
Portland August air quality, year by year
Portland August air quality by year (Portland-Vancouver-Hillsboro, OR-WA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 41 | 1 | 101 | O3 |
| 2020cleanest | 31 | 37 | 1 | 122 | O3 |
| 2021 | 31 | 42 | 1 | 161 | O3 |
| 2022 | 31 | 41 | 1 | 101 | O3 |
| 2023worst | 31 | 50 | 5 | 153 | O3 |
| 2024 | 31 | 44 | 2 | 126 | O3 |
| 2025 | 31 | 44 | 2 | 119 | O3 |
What August air means in Portland
A typical August day in Portland sits in the Good range (median AQI 42), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 17 of August days (6.0%) reached AQI 101+ in 2019–2025.
August's median AQI of 42 is in line with Portland's whole-year median of 41, 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; 6.0% of its August days topped AQI 100 versus 3.5% nationally (above 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 (PM2.5). 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-Vancouver-Hillsboro, OR-WA), 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.