SmogRank / United States / California / Sebastopol

Sebastopol, month by month

Sebastopol has a measured daily mean on 1,140 days since 1 January 2023. Its worst month was January 2026, at 52 US AQI (9.6 µg/m³), 1,149th of 2,617 cities on that month's world ranking. Its cleanest was July 2025, at 10 US AQI (1.8 µg/m³). 2025 averaged 24 US AQI (4.3 µg/m³), against 29 US AQI (5.2 µg/m³) in 2023.

Every month since 2023

202632 so far270 days measured2,524th of 2,793 in the world
Jan52#1,149Feb31#2,522Mar26#2,720Apr28#2,472May31#2,118Jun23#2,271Jul47#1,768Aug22#2,838Sep24#2,633Oct29#2,112
202524 for the year332 days measured2,613th of 2,681 in the world
Jan46#1,359Feb26#2,429Mar24#2,586Apr22#2,801May23#2,545Jun21#2,423Jul10#2,887Aug13#2,897Sep18#3,036Oct14#2,591Nov15 daysDec41#2,059
2024too few days for a mean (a year needs 257)240 days measured
Jan25#2,178Feb21#2,352MarnoneAprnoneMay6 daysJun18 daysJul19#2,501Aug15#2,006Sep11#2,007Oct19#1,975Nov27#2,336Dec44#1,396
202329 for the year298 days measured1,242nd of 1,355 in the world
Jan34#954Feb1 dayMar9 daysApr18#1,538May21#1,543Jun23#1,483Jul27#1,249Aug34#1,612Sep43#1,233Oct21#1,946Nov33#1,719Dec38#1,618
Each square is a month's mean PM2.5 in US AQI from Sebastopol'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 Sebastopol 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

7 months
MonthWhy
Nov 202515 of 30 days measured; a month needs 21. The others: 15 with under 18 hours of readings or readings that failed our checks.
Jun 202418 of 30 days measured; a month needs 21. The others: 12 with under 18 hours of readings or readings that failed our checks.
May 20246 of 31 days measured; a month needs 22. The others: 25 with under 18 hours of readings or readings that failed our checks.
Apr 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Mar 2024No day measured. The others: 1 missing from OpenAQ's archive, 30 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.

Sebastopol's worst months

MonthUS AQIDays measuredWorld rankEpisode
January 2026 529.6 µg/m³31 of 311,149thof 2,617–
July 2026 478.4 µg/m³31 of 311,768thof 2,784–
January 2025 468.2 µg/m³30 of 311,359thof 2,474–
December 2024 447.9 µg/m³30 of 311,396thof 2,616–
September 2023 437.7 µg/m³30 of 301,233rdof 2,176California and Oregon, United States, September 2023
December 2025 417.3 µg/m³31 of 312,059thof 3,006–

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.

Sebastopol's worst days

DayUS AQIEpisode
30 Jul 2026 16372.0 µg/m³–
31 Jul 2026 15764.2 µg/m³–
20 Sept 2023 11641.4 µg/m³California and Oregon, United States, September 2023
21 Sept 2023 10838.3 µg/m³California and Oregon, United States, September 2023
22 Sept 2023 9633.4 µg/m³California and Oregon, United States, September 2023
30 Aug 2023 8426.8 µg/m³North-western United States and Canada, August 2023
11 Dec 2024 7220.6 µg/m³–
5 Dec 2025 7019.2 µg/m³–
19 Sept 2023 6918.6 µg/m³California and Oregon, United States, September 2023
15 Jan 2026 6918.5 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, Sebastopol, 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/sebastopol/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.

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

Updated 2026-10-12 21:07 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).