Tacoma Air Quality in December
Across 2019–2025, Tacoma's December air quality had a median AQI of 56 (Moderate) over 217 monitored days in the Seattle-Tacoma-Bellevue, WA area. 1.8% of December days (4 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 81.1% of days. The cleanest December on record here was 2025 (median AQI 42, 0 days above 100) and the worst was 2022 (median 57, 3 days above 100, peak AQI 108).
- Good: 34.1%
- Moderate: 64.1%
- Unhealthy for Sensitive Groups: 1.8%
- Unhealthy or worse: 0.0%
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How is the air in Tacoma in December?
Moderate on a typical day: median AQI 56 across 2019–2025, with 1.8% of December days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓34.1% of December days were Good (AQI 0–50), 64.1% Moderate (51–100).
- ✓4 days of 217 reached AQI 101+; the December peak was 108.
- ✓Best December: 2025; worst December: 2022.
Frequently asked questions
What is the air quality like in Tacoma in December?▾
Across 2019–2025, the median daily AQI in Tacoma in December was 56 (Moderate). 34.1% of days were Good, 64.1% Moderate, and 1.8% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is December a good time for outdoor exercise in Tacoma?▾
A typical December day in Tacoma is Moderate (median AQI 56): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 56 of December 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 Tacoma's December air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 81.1% of December days in Tacoma. The highest December AQI recorded in 2019–2025 was 108 (Unhealthy for Sensitive Groups), in 2022.
Tacoma December air quality, year by year
Tacoma December air quality by year (Seattle-Tacoma-Bellevue, WA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 64 | 0 | 90 | PM2.5 |
| 2020 | 31 | 57 | 0 | 97 | PM2.5 |
| 2021 | 31 | 55 | 1 | 104 | PM2.5 |
| 2022worst | 31 | 57 | 3 | 108 | PM2.5 |
| 2023 | 31 | 54 | 0 | 85 | PM2.5 |
| 2024 | 31 | 54 | 0 | 86 | PM2.5 |
| 2025cleanest | 31 | 42 | 0 | 85 | PM2.5 |
What December air means in Tacoma
A typical December day in Tacoma is Moderate (median AQI 56): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 56 of December days (1.8%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
December's median AQI of 56 is above Tacoma's whole-year median of 49, making it one of the area's dirtier periods. Nationally, the median December AQI across every EPA metro area (95,590 metro-days, 2019–2025) is 39, so Tacoma runs above the national December norm; 1.8% of its December days topped AQI 100 versus 0.7% nationally (above average).
December is part of Tacoma's winter season (December, January, February); the winter page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Tacoma
The latest EPA AirNow observation puts Tacoma's AQI at 41 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Tacoma 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.