Seattle Air Quality in January
Across 2019–2025, Seattle's January air quality had a median AQI of 58 (Moderate) over 217 monitored days in the Seattle-Tacoma-Bellevue, WA area. 1.8% of January days (4 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 86.6% of days. The cleanest January on record here was 2020 (median AQI 46, 0 days above 100) and the worst was 2019 (median 60, 2 days above 100, peak AQI 142).
- Good: 29.5%
- Moderate: 68.7%
- Unhealthy for Sensitive Groups: 1.8%
- Unhealthy or worse: 0.0%
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How is the air in Seattle in January?
Moderate on a typical day: median AQI 58 across 2019–2025, with 1.8% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓29.5% of January days were Good (AQI 0–50), 68.7% Moderate (51–100).
- ✓4 days of 217 reached AQI 101+; the January peak was 142.
- ✓Best January: 2020; worst January: 2019.
Frequently asked questions
What is the air quality like in Seattle in January?▾
Across 2019–2025, the median daily AQI in Seattle in January was 58 (Moderate). 29.5% of days were Good, 68.7% Moderate, and 1.8% 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 Seattle?▾
A typical January day in Seattle is Moderate (median AQI 58): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 56 of January 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 Seattle's January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 86.6% of January days in Seattle. The highest January AQI recorded in 2019–2025 was 142 (Unhealthy for Sensitive Groups), in 2019.
Seattle January air quality, year by year
Seattle January air quality by year (Seattle-Tacoma-Bellevue, WA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 31 | 60 | 2 | 142 | PM2.5 |
| 2020cleanest | 31 | 46 | 0 | 72 | PM2.5 |
| 2021 | 31 | 61 | 1 | 108 | PM2.5 |
| 2022 | 31 | 61 | 1 | 107 | PM2.5 |
| 2023 | 31 | 53 | 0 | 76 | PM2.5 |
| 2024 | 31 | 53 | 0 | 96 | PM2.5 |
| 2025 | 31 | 70 | 0 | 89 | PM2.5 |
What January air means in Seattle
A typical January day in Seattle is Moderate (median AQI 58): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 56 of January days (1.8%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
January's median AQI of 58 is above Seattle's whole-year median of 49, 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 Seattle runs above the national January norm; 1.8% of its January days topped AQI 100 versus 0.7% nationally (above average).
January is part of Seattle's winter season (December, January, February); the winter page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Seattle
The latest EPA AirNow observation puts Seattle's AQI at 37 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Seattle air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Seattle-Tacoma-Bellevue, 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.