SmogRank / United States / Oregon / Forest Grove

Forest Grove, month by month

Forest Grove has a measured daily mean on 1,223 days since 1 January 2023. Its worst month was August 2026, at 43 US AQI (7.7 µg/m³), 1,760th of 2,896 cities on that month's world ranking. Its cleanest was June 2024, at 12 US AQI (2.2 µg/m³). 2025 averaged 17 US AQI (3.1 µg/m³), against 21 US AQI (3.8 µg/m³) in 2024.

Every month since 2023

202621 so far265 days measured2,764th of 2,793 in the world
Jan26#2,399Feb16#2,822Mar15#2,934Apr14#2,914May14#2,850Jun13#2,471Jul14#2,774Aug43#1,760Sep23#2,676Oct25#2,348
202517 for the year352 days measured2,672nd of 2,681 in the world
Jan30#2,142Feb19#2,581Mar16#2,820Apr15#2,930May14#2,799Jun13#2,501Jul13#2,878Aug15#2,893Sep17#3,057Oct19#2,525Nov20#2,610Dec18#2,938
202421 for the year306 days measured2,059th of 2,097 in the world
Jan19 daysFeb19#2,378Mar17#1,627Apr13#2,482May12#2,650Jun12#2,539Jul17#2,528Aug24#1,952Sep17 daysOct15 daysNov31#2,171Dec27#2,303
202327 for the year300 days measured1,279th of 1,355 in the world
Jan35#943Feb1 dayMar9 daysApr15#1,587May15#1,586Jun16#1,577Jul17#1,392Aug42#1,146Sep25#2,053Oct34#1,413Nov41#1,320Dec27#2,033
Each square is a month's mean PM2.5 in US AQI from Forest Grove'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 Forest Grove 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

5 months
MonthWhy
Oct 202415 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks.
Sep 202417 of 30 days measured; a month needs 21. The others: 13 with under 18 hours of readings or readings that failed our checks.
Jan 202419 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks.
Mar 20239 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive, 2 with under 18 hours of readings or readings that failed our checks.
Feb 20231 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.

Forest Grove's worst months

MonthUS AQIDays measuredWorld rankEpisode
August 2026 437.7 µg/m³31 of 311,760thof 2,896North-western United States and Canada, 4 to 22 August 2026
August 2023 427.5 µg/m³31 of 311,146thof 1,980North-western United States and Canada, August 2023
November 2023 417.4 µg/m³30 of 301,320thof 2,243–
January 2023 356.3 µg/m³24 of 31943rdof 1,261–
October 2023 346.2 µg/m³31 of 311,413thof 2,012–
November 2024 315.5 µg/m³30 of 302,171stof 2,624–

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.

Forest Grove's worst days

DayUS AQIEpisode
20 Oct 2024 17792.9 µg/m³–
20 Aug 2023 11039.2 µg/m³North-western United States and Canada, August 2023
5 Aug 2026 10637.5 µg/m³North-western United States and Canada, 4 to 22 August 2026
6 Aug 2026 9331.6 µg/m³North-western United States and Canada, 4 to 22 August 2026
6 Sept 2024 7622.5 µg/m³–
4 Aug 2026 7321.0 µg/m³North-western United States and Canada, 4 to 22 August 2026
10 Nov 2024 7019.4 µg/m³–
31 Jan 2023 7019.1 µg/m³–
25 Aug 2023 6818.3 µg/m³North-western United States and Canada, August 2023
9 Nov 2024 6818.1 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, Forest Grove, 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/forest-grove/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.

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

Updated 2026-10-12 23:07 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).