SmogRank / United States / Washington / Mount Vernon

Mount Vernon, month by month

Mount Vernon has a measured daily mean on 1,270 days since 1 January 2023. Its worst month was May 2023, at 37 US AQI (6.6 µg/m³), 1,203rd of 1,600 cities on that month's world ranking. Its cleanest was December 2025, at 6 US AQI (1.0 µg/m³). 2025 averaged 12 US AQI (2.1 µg/m³), against 17 US AQI (3.0 µg/m³) in 2024.

Every month since 2023

202616 so far265 days measured2,787th of 2,791 in the world

Jan13#2,599Feb19 daysMar7#2,969 Apr13#2,924 May16#2,833 Jun11#2,485 Jul21#2,723 Aug32#2,570 Sep21#2,809 Oct23#2,457

202512 for the year352 days measured2,681st of 2,681 in the world

Jan17#2,447 Feb8#2,629 Mar7#2,862 Apr11#2,947 May9#2,826 Jun11#2,505 Jul14#2,872 Aug18#2,866 Sep19#3,013 Oct13#2,601 Nov8#2,713 Dec6#3,005

202417 for the year352 days measured2,089th of 2,097 in the world

Jan19#2,314 Feb21#2,340 Mar17#1,618 Apr17#2,430 May16#2,592 Jun15#2,516 Jul25#2,368 Aug26#1,914 Sep14#1,999 Oct8#2,018 Nov10#2,621 Dec8#2,614

202327 for the year301 days measured1,279th of 1,355 in the world

Jan20#1,204Feb1 dayMar11 daysApr18#1,547 May37#1,203 Jun21#1,515 Jul24#1,297 Aug34#1,581 Sep27#2,014 Oct27#1,785 Nov34#1,654 Dec21#2,150

Each square is a month's mean PM2.5 in US AQI from Mount Vernon's measured days, with its place on that month's world ranking under it. A month has a mean once 70% of its days are measured, the rule the monthly rankings use; under that, the square gives the days measured. Each square opens that month's ranking with Mount Vernon marked; each year, the year's. A dashed square is the running month, so far.

Good0–50

Moderate51–100

Sensitive groups101–150

Unhealthy151–200

Very unhealthy201–300

Hazardous301+

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

Months without a mean, and why

3 months

Month	Why
Feb 2026	19 of 28 days measured; a month needs 20. The others: 9 with under 18 hours of readings or readings that failed our checks.
Mar 2023	11 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive.
Feb 2023	1 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive, 2 with under 18 hours of readings or readings that failed our checks.

A day counts once 18 hours of it are measured; a month needs 70% of its days.

Mount Vernon's worst months

Month	US AQI	Days measured	World rank
May 2023	376.6 µg/m³	30 of 31	1,203rdof 1,600
August 2023	346.2 µg/m³	31 of 31	1,581stof 1,980
November 2023	346.2 µg/m³	25 of 30	1,654thof 2,243
August 2026	325.7 µg/m³	30 of 31	2,570thof 2,896
October 2023	274.9 µg/m³	31 of 31	1,785thof 2,012
September 2023	274.8 µg/m³	30 of 30	2,014thof 2,176

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.

Mount Vernon's worst days

Day	US AQI
5 Aug 2026	7823.8 µg/m³
26 Aug 2023	7622.4 µg/m³
27 Aug 2023	6918.7 µg/m³
5 Jul 2023	6717.5 µg/m³
7 May 2023	6617.0 µg/m³
6 Aug 2026	6616.9 µg/m³
28 Aug 2023	6315.5 µg/m³
25 Aug 2023	6315.3 µg/m³
22 Jul 2026	6215.2 µg/m³
20 Aug 2023	6215.0 µg/m³

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, Mount Vernon, 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/mount-vernon-washington/history (accessed 12 Oct 2026).

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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.

Mount Vernon now: the last 24 hours, its ranks today and the last 12 months day by day.

Updated 2026-10-12 20:07 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).