Washington Air Quality in Winter
Across 2019–2025, Washington's winter (December–February) air quality had a median AQI of 50 (Good) over 632 monitored days in the Washington-Arlington-Alexandria, DC-VA-MD-WV area. 0.0% of winter days (0 of 632) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 78.8% of days. The cleanest winter on record here was 2020 (median AQI 43, 0 days above 100) and the worst was 2022 (median 54, 0 days above 100, peak AQI 74).
- Good: 50.3%
- Moderate: 49.7%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Washington in winter?
Good on a typical day: median AQI 50 across 2019–2025, with 0.0% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓50.3% of winter days were Good (AQI 0–50), 49.7% Moderate (51–100).
- ✓0 days of 632 reached AQI 101+; the winter peak was 94.
- ✓Cleanest month: January; worst month: February.
Frequently asked questions
What is the air quality like in Washington in winter?▾
Across 2019–2025, the median daily AQI in Washington in winter was 50 (Good). 50.3% of days were Good, 49.7% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 632 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in Washington?▾
A typical winter day in Washington sits in the Good range (median AQI 50), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Which pollutant causes Washington's winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 78.8% of winter days in Washington. The highest winter AQI recorded in 2019–2025 was 94 (Moderate), in 2022.
Washington winter air quality, year by year
Washington winter air quality by year (Washington-Arlington-Alexandria, DC-VA-MD-WV, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 90 | 48 | 0 | 94 | PM2.5 |
| 2020cleanest | 91 | 43 | 0 | 83 | PM2.5 |
| 2021 | 90 | 54 | 0 | 84 | PM2.5 |
| 2022worst | 90 | 54 | 0 | 74 | PM2.5 |
| 2023 | 90 | 48 | 0 | 74 | PM2.5 |
| 2024 | 91 | 47 | 0 | 75 | PM2.5 |
| 2025 | 90 | 44 | 0 | 77 | PM2.5 |
What winter air means in Washington
A typical winter day in Washington sits in the Good range (median AQI 50), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Winter's median AQI of 50 is in line with Washington's whole-year median of 52, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so Washington runs above the national Winter norm; 0.0% of its Winter days topped AQI 100 versus 0.6% nationally (about the same).
Within the season, January is the cleanest month (median AQI 48, 0.0% of days above 100) and February the worst (median 51, 0.0% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Washington
The latest EPA AirNow observation puts Washington's AQI at 41 (PM2.5). The figures above are multi-year season statistics, not today's reading.
View current Washington air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Washington-Arlington-Alexandria, DC-VA-MD-WV), 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.