Portland, ME Air Quality in Spring
Across 2019–2025, Portland's spring (March–May) air quality had a median AQI of 43 (Good) over 644 monitored days in the Portland-South Portland, ME area. 0.0% of spring days (0 of 644) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 80.6% of days. The cleanest spring on record here was 2021 (median AQI 40, 0 days above 100) and the worst was 2019 (median 46, 0 days above 100, peak AQI 81).
- Good: 85.1%
- Moderate: 14.9%
- 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 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 spring?
Good on a typical day: median AQI 43 across 2019–2025, with 0.0% of spring days above AQI 100. Ground-level ozone is the main driver.
- ✓85.1% of spring days were Good (AQI 0–50), 14.9% Moderate (51–100).
- ✓0 days of 644 reached AQI 101+; the spring peak was 84.
- ✓Cleanest month: May; worst month: April.
Frequently asked questions
What is the air quality like in Portland in spring?▾
Across 2019–2025, the median daily AQI in Portland in spring was 43 (Good). 85.1% of days were Good, 14.9% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 644 monitored days in EPA's Air Quality System.
Is spring a good time for outdoor exercise in Portland?▾
A typical spring 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; fewer than 1% of spring days reached AQI 101+ in 2019–2025.
Which pollutant causes Portland's spring air quality problems?▾
Ground-level ozone set the daily AQI on 80.6% of spring days in Portland. The highest spring AQI recorded in 2019–2025 was 84 (Moderate), in 2019.
Portland spring air quality, year by year
Portland spring air quality by year (Portland-South Portland, ME, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 92 | 46 | 0 | 81 | PM2.5 |
| 2020 | 92 | 43 | 0 | 61 | O3 |
| 2021cleanest | 92 | 40 | 0 | 84 | O3 |
| 2022 | 92 | 41 | 0 | 64 | O3 |
| 2023 | 92 | 44 | 0 | 80 | O3 |
| 2024 | 92 | 40 | 0 | 74 | O3 |
| 2025 | 92 | 44 | 0 | 84 | O3 |
What spring air means in Portland
A typical spring 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; fewer than 1% of spring days reached AQI 101+ in 2019–2025.
Spring'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 Spring AQI across every EPA metro area (307,196 metro-days, 2019–2025) is 43, so Portland runs in line with the national Spring norm; 0.0% of its Spring days topped AQI 100 versus 0.8% nationally (about the same).
Within the season, May is the cleanest month (median AQI 40, 0.0% of days above 100) and April the worst (median 43, 0.0% above 100).
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 season 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.