Portland, ME Air Quality in July
Across 2019–2025, Portland's July air quality had a median AQI of 52 (Moderate) over 217 monitored days in the Portland-South Portland, ME area. 1.8% of July days (4 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 61.8% of days. The cleanest July on record here was 2021 (median AQI 31, 0 days above 100) and the worst was 2022 (median 44, 2 days above 100, peak AQI 126).
- Good: 46.1%
- Moderate: 52.1%
- Unhealthy for Sensitive Groups: 1.8%
- 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
As an Amazon Associate, we earn from qualifying purchases.
How is the air in Portland in July?
Moderate on a typical day: median AQI 52 across 2019–2025, with 1.8% of July days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓46.1% of July days were Good (AQI 0–50), 52.1% Moderate (51–100).
- ✓4 days of 217 reached AQI 101+; the July peak was 126.
- ✓Best July: 2021; worst July: 2022.
Frequently asked questions
What is the air quality like in Portland in July?▾
Across 2019–2025, the median daily AQI in Portland in July was 52 (Moderate). 46.1% of days were Good, 52.1% Moderate, and 1.8% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is July a good time for outdoor exercise in Portland?▾
A typical July day in Portland is Moderate (median AQI 52): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 56 of July days (1.8%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Portland's July air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 61.8% of July days in Portland. The highest July AQI recorded in 2019–2025 was 126 (Unhealthy for Sensitive Groups), in 2022.
Portland July air quality, year by year
Portland July 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 | 55 | 1 | 115 | PM2.5 |
| 2020 | 31 | 48 | 0 | 87 | PM2.5 |
| 2021cleanest | 31 | 31 | 0 | 92 | O3 |
| 2022worst | 31 | 44 | 2 | 126 | O3 |
| 2023 | 31 | 60 | 0 | 100 | PM2.5 |
| 2024 | 31 | 53 | 0 | 97 | PM2.5 |
| 2025 | 31 | 51 | 1 | 114 | PM2.5 |
What July air means in Portland
A typical July day in Portland is Moderate (median AQI 52): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 56 of July days (1.8%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
July's median AQI of 52 is above Portland's whole-year median of 40, making it one of the area's dirtier periods. Nationally, the median July AQI across every EPA metro area (103,858 metro-days, 2019–2025) is 47, so Portland runs above the national July norm; 1.8% of its July days topped AQI 100 versus 3.6% nationally (below average).
July 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.