SmogRank / United States / District of Columbia / Washington
Washington, month by month
Washington has a measured daily mean on 1,368 days since 1 January 2023. Its worst month was June 2023, at 76 US AQI (22.6 µg/m³), 221st of 1,603 cities on that month's world ranking. Its cleanest was October 2025, at 27 US AQI (4.9 µg/m³). 2025 averaged 41 US AQI (7.3 µg/m³), against 38 US AQI (6.9 µg/m³) in 2024.
Every month since 2023
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
Washington's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| June 2023 | 7622.6 µg/m³ | 221stof 1,603 | Eastern United States and Canada, June and July 2023 Eastern United States and Canada, May and June 2023 |
| July 2026 | 6516.8 µg/m³ | 430thof 2,784 | Northern United States and Canada, July 2026 |
| July 2023 | 5913.3 µg/m³ | 255thof 1,432 | United States and Canada, July 2023 North-eastern United States, 4 to 5 July 2023and 1 more |
| July 2025 | 5712.2 µg/m³ | 791stof 2,889 | North-eastern United States, July 2025 |
| February 2026 | 5410.5 µg/m³ | 1,290thof 2,866 | – |
| June 2025 | 5310.4 µg/m³ | 1,179thof 2,508 | – |
Monthly means over the days measured; finished months only. World rank: its place on that month's world ranking of every city with enough days. Each month opens that ranking.
Washington's worst days
| Day | US AQI | Episode |
|---|---|---|
| 8 Jun 2023 | 193115.5 µg/m³ | Eastern United States and Canada, May and June 2023 |
| 17 Jul 2026 | 187107.5 µg/m³ | Northern United States and Canada, July 2026 |
| 29 Jun 2023 | 16879.6 µg/m³ | Eastern United States and Canada, June and July 2023 |
| 7 Jun 2023 | 16271.2 µg/m³ | Eastern United States and Canada, May and June 2023 |
| 5 Jul 2025 | 15966.2 µg/m³ | North-eastern United States, July 2025 |
| 4 Jul 2025 | 13448.8 µg/m³ | North-eastern United States, July 2025 |
| 5 Jul 2026 | 12746.0 µg/m³ | – |
| 18 Jul 2026 | 12745.9 µg/m³ | Northern United States and Canada, July 2026 |
| 30 Jun 2023 | 10738.1 µg/m³ | Eastern United States and Canada, June and July 2023 |
| 28 Jun 2023 | 9834.4 µg/m³ | Eastern United States and Canada, June and July 2023 |
Daily means, the highest since 1 Jan 2023; the WHO's daily guideline is 15 µg/m³. Each date opens that day's world ranking, and each episode the bad-air spell it was part of.
Use this history
SmogRank, PM2.5 monthly and daily means, Washington, United States, 1 Jan 2023 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/washington/history (accessed 12 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.
Washington now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 17:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index. Some low-cost readings: Sensor.Community, ODbL (data and licence). Some readings: Uzhydromet (Uzbekistan's Hydrometeorological Service); Department of Environment, Nepal; Vietnam's government monitors; Aurassure; Umhverfisstofnun (Environment Agency of Iceland); RMCAB (Secretaría Distrital de Ambiente, Bogotá); Love My Air (City and County of Denver), no reuse terms published (why we use them).