Portland, OR Air Quality in January
Across 2019–2025, Portland's January air quality had a median AQI of 46 (Good) over 217 monitored days in the Portland-Vancouver-Hillsboro, OR-WA area. 0.5% of January days (1 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 76.0% of days. The cleanest January on record here was 2020 (median AQI 33, 0 days above 100) and the worst was 2019 (median 55, 1 day above 100, peak AQI 128).
- Good: 53.9%
- Moderate: 45.6%
- Unhealthy for Sensitive Groups: 0.5%
- Unhealthy or worse: 0.0%
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How is the air in Portland in January?
Good on a typical day: median AQI 46 across 2019–2025, with 0.5% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓53.9% of January days were Good (AQI 0–50), 45.6% Moderate (51–100).
- ✓1 day of 217 reached AQI 101+; the January peak was 128.
- ✓Best January: 2020; worst January: 2019.
Frequently asked questions
What is the air quality like in Portland in January?▾
Across 2019–2025, the median daily AQI in Portland in January was 46 (Good). 53.9% of days were Good, 45.6% Moderate, and 0.5% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is January a good time for outdoor exercise in Portland?▾
A typical January day in Portland sits in the Good range (median AQI 46), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of January days reached AQI 101+ in 2019–2025.
Which pollutant causes Portland's January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 76.0% of January days in Portland. The highest January AQI recorded in 2019–2025 was 128 (Unhealthy for Sensitive Groups), in 2019.
Portland January air quality, year by year
Portland January 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 |
|---|---|---|---|---|---|
| 2019worst | 31 | 55 | 1 | 128 | PM2.5 |
| 2020cleanest | 31 | 33 | 0 | 66 | O3 |
| 2021 | 31 | 53 | 0 | 75 | PM2.5 |
| 2022 | 31 | 54 | 0 | 77 | PM2.5 |
| 2023 | 31 | 41 | 0 | 81 | PM2.5 |
| 2024 | 31 | 33 | 0 | 66 | PM2.5 |
| 2025 | 31 | 56 | 0 | 88 | PM2.5 |
What January air means in Portland
A typical January day in Portland sits in the Good range (median AQI 46), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of January days reached AQI 101+ in 2019–2025.
January's median AQI of 46 is above Portland's whole-year median of 41, making it one of the area's dirtier periods. Nationally, the median January AQI across every EPA metro area (95,602 metro-days, 2019–2025) is 39, so Portland runs above the national January norm; 0.5% of its January days topped AQI 100 versus 0.7% nationally (about the same).
January is part of Portland's winter season (December, January, February); the winter 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.