SmogRank / United States / California / Pasadena

Pasadena, month by month

Pasadena, California has a measured daily mean on 144 days since 25 February 2025. Its worst month was June 2025, at 64 US AQI (16.2 µg/m³), 360th of 2,508 cities on that month's world ranking. Its cleanest was March 2025, at 42 US AQI (7.6 µg/m³).

Every month since 2025

2026too few days for a mean (a year needs 199)11 days measured
JannoneFebnoneMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOct17#2,687
2025too few days for a mean (a year needs 256)133 days measured
JanFeb4 daysMar42#1,992Apr55#870May59#468Jun64#360Jul7 daysAugnoneSepnoneOctnoneNovnoneDecnone
Each square is a month's mean PM2.5 in US AQI from Pasadena'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 Pasadena 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

16 months
MonthWhy
Sep 2026No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Aug 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jul 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jun 2026No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
May 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Apr 2026No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Mar 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Feb 2026No day measured. The others: 28 with under 18 hours of readings or readings that failed our checks.
Jan 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Dec 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Nov 2025No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Oct 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Sep 2025No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Aug 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jul 20257 of 31 days measured; a month needs 22. The others: 24 with under 18 hours of readings or readings that failed our checks.
Feb 20254 of 28 days measured; a month needs 20.

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

Pasadena's worst months

MonthUS AQIDays measuredWorld rank
June 2025 6416.2 µg/m³30 of 30360thof 2,508
May 2025 5913.6 µg/m³31 of 31468thof 2,826
April 2025 5511.3 µg/m³30 of 30870thof 2,951
March 2025 427.6 µg/m³31 of 311,992ndof 2,862

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.

Pasadena's worst days

DayUS AQI
5 Jul 2025 16169.5 µg/m³
14 Apr 2025 7924.2 µg/m³
13 Apr 2025 7823.5 µg/m³
23 May 2025 7622.6 µg/m³
10 Jun 2025 7421.4 µg/m³
14 Jun 2025 7421.4 µg/m³
22 Apr 2025 7320.9 µg/m³
18 Jun 2025 7119.8 µg/m³
27 Jun 2025 7119.8 µg/m³
30 Apr 2025 7119.7 µg/m³

Daily means, the highest since 25 Feb 2025; 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, Pasadena, California, United States, 25 Feb 2025 – 11 Oct 2026. Monitor data from AirGradient via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/us/pasadena-california/history (accessed 13 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.

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

Updated 2026-10-13 01:07 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).