Washington Air Quality in May
Across 2019–2025, Washington's May air quality had a median AQI of 49 (Good) over 217 monitored days in the Washington-Arlington-Alexandria, DC-VA-MD-WV area. 2.3% of May days (5 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 63.6% of days. The cleanest May on record here was 2020 (median AQI 45, 0 days above 100) and the worst was 2021 (median 53, 3 days above 100, peak AQI 140).
- Good: 53.5%
- Moderate: 44.2%
- Unhealthy for Sensitive Groups: 2.3%
- Unhealthy or worse: 0.0%
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How is the air in Washington in May?
Good on a typical day: median AQI 49 across 2019–2025, with 2.3% of May days above AQI 100. Ground-level ozone is the main driver.
- ✓53.5% of May days were Good (AQI 0–50), 44.2% Moderate (51–100).
- ✓5 days of 217 reached AQI 101+; the May peak was 140.
- ✓Best May: 2020; worst May: 2021.
Frequently asked questions
What is the air quality like in Washington in May?▾
Across 2019–2025, the median daily AQI in Washington in May was 49 (Good). 53.5% of days were Good, 44.2% Moderate, and 2.3% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is May a good time for outdoor exercise in Washington?▾
A typical May day in Washington sits in the Good range (median AQI 49), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 43 of May days (2.3%) reached AQI 101+ in 2019–2025.
Which pollutant causes Washington's May air quality problems?▾
Ground-level ozone set the daily AQI on 63.6% of May days in Washington. The highest May AQI recorded in 2019–2025 was 140 (Unhealthy for Sensitive Groups), in 2021.
Washington May air quality, year by year
Washington May 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 | 31 | 57 | 0 | 87 | PM2.5 |
| 2020cleanest | 31 | 45 | 0 | 58 | O3 |
| 2021worst | 31 | 53 | 3 | 140 | O3 |
| 2022 | 31 | 47 | 0 | 87 | O3 |
| 2023 | 31 | 54 | 1 | 119 | O3 |
| 2024 | 31 | 48 | 1 | 105 | O3 |
| 2025 | 31 | 45 | 0 | 93 | O3 |
What May air means in Washington
A typical May day in Washington sits in the Good range (median AQI 49), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 43 of May days (2.3%) reached AQI 101+ in 2019–2025.
May's median AQI of 49 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 May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Washington runs above the national May norm; 2.3% of its May days topped AQI 100 versus 1.3% nationally (about the same).
May is part of Washington's spring season (March, April, May); the spring page pools all three months.
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 month 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.