SmogRank / United States / Washington / Issaquah

Issaquah, month by month

Issaquah has a measured daily mean on 342 days since 7 July 2023. Its worst month was August 2023, at 57 US AQI (12.1 µg/m³), 329th of 1,980 cities on that month's world ranking. Its cleanest was May 2024, at 6 US AQI (1.1 µg/m³).

Every month since 2023

2026too few days for a mean (a year needs 199)0 days measured
JannoneFebnoneMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnone
2025too few days for a mean (a year needs 256)0 days measured
JannoneFebnoneMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnoneNovnoneDecnone
2024too few days for a mean (a year needs 257)172 days measured
Jan9#2,380Feb7#2,483Mar7#1,694Apr7#2,515May6#2,678Jun7#2,560JulnoneAugnoneSepnoneOctnoneNovnoneDecnone
2023too few days for a mean (a year needs 256)170 days measured
JanFebMarAprMayJunJul18#1,382Aug57#329Sep21#2,114Oct21#1,946Nov26#2,030Dec15#2,216
Each square is a month's mean PM2.5 in US AQI from Issaquah'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 Issaquah marked; each year, the year's.
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

28 months
MonthWhy
Oct 2026No day measured.
Sep 2026No day measured.
Aug 2026No day measured.
Jul 2026No day measured.
Jun 2026No day measured.
May 2026No day measured.
Apr 2026No day measured.
Mar 2026No day measured.
Feb 2026No day measured.
Jan 2026No day measured.
Dec 2025No day measured.
Nov 2025No day measured.
Oct 2025No day measured.
Sep 2025No day measured.
Aug 2025No day measured.
Jul 2025No day measured.
Jun 2025No day measured.
May 2025No day measured.
Apr 2025No day measured.
Mar 2025No day measured.
Feb 2025No day measured.
Jan 2025No day measured.
Dec 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Nov 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Oct 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Sep 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Aug 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jul 2024No day measured. The others: 31 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.

Issaquah's worst months

MonthUS AQIDays measuredWorld rankEpisode
August 2023 5712.1 µg/m³30 of 31329thof 1,980North-western United States and Canada, August 2023
November 2023 264.7 µg/m³30 of 302,030thof 2,243–
September 2023 213.8 µg/m³30 of 302,114thof 2,176–
October 2023 213.7 µg/m³31 of 311,946thof 2,012–
July 2023 183.3 µg/m³22 of 311,382ndof 1,432–
December 2023 152.7 µg/m³27 of 312,216thof 2,247–

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.

Issaquah's worst days

DayUS AQIEpisode
20 Aug 2023 15560.7 µg/m³North-western United States and Canada, August 2023
21 Aug 2023 15357.8 µg/m³North-western United States and Canada, August 2023
27 Aug 2023 9934.9 µg/m³North-western United States and Canada, August 2023
2 Aug 2023 9532.5 µg/m³–
26 Aug 2023 9030.1 µg/m³North-western United States and Canada, August 2023
28 Aug 2023 7119.9 µg/m³North-western United States and Canada, August 2023
25 Aug 2023 6918.7 µg/m³North-western United States and Canada, August 2023
29 Nov 2023 5813.0 µg/m³–
1 Nov 2023 5511.4 µg/m³–
24 Aug 2023 5511.2 µg/m³North-western United States and Canada, August 2023

Daily means, the highest since 7 Jul 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, Issaquah, United States, 7 Jul 2023 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/issaquah/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.

Issaquah 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).