SmogRank / United States / California / Lancaster

Lancaster, month by month

Lancaster has a measured daily mean on 1,303 days since 11 January 2023. Its worst month was August 2025, at 44 US AQI (7.9 µg/m³), 1,855th of 2,901 cities on that month's world ranking. Its cleanest was February 2024, at 13 US AQI (2.3 µg/m³). 2025 averaged 28 US AQI (5.0 µg/m³), against 29 US AQI (5.2 µg/m³) in 2024.

Every month since 2023

202628 so far284 days measured2,624th of 2,791 in the world

Jan17#2,574 Feb22#2,729 Mar34#2,528 Apr26#2,592 May38#1,653 Jun31#2,037 Jul30#2,540 Aug32#2,570 Sep25#2,554 Oct24#2,395

202528 for the year358 days measured2,528th of 2,681 in the world

Jan28#2,211 Feb17#2,607 Mar20#2,723 Apr29#2,479 May34#1,862 Jun35#2,128 Jul32#2,420 Aug44#1,855 Sep29#2,453 Oct23#2,346 Nov17#2,657 Dec22#2,855

202429 for the year361 days measured1,923rd of 2,097 in the world

Jan14#2,368 Feb13#2,462 Mar18#1,601 Apr27#2,002 May32#2,073 Jun34#1,967 Jul43#1,459 Aug33#1,752 Sep37#1,294 Oct34#1,409 Nov29#2,214 Dec32#2,116

202323 for the year300 days measured1,319th of 1,355 in the world

Jan7 daysFeb13 daysMar21 daysApr24#1,430 May26#1,465 Jun30#1,385 Jul31#1,162 Aug24#1,885 Sep32#1,837 Oct21#1,946 Nov21#2,154Dec18 days

Each square is a month's mean PM2.5 in US AQI from Lancaster'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 Lancaster 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

4 months

Month	Why
Dec 2023	18 of 31 days measured; a month needs 22. The others: 13 with under 18 hours of readings or readings that failed our checks.
Mar 2023	21 of 31 days measured; a month needs 22. The others: 10 missing from OpenAQ's archive.
Feb 2023	13 of 28 days measured; a month needs 20. The others: 12 missing from OpenAQ's archive, 3 with under 18 hours of readings or readings that failed our checks.
Jan 2023	7 of 31 days measured; a month needs 22. The others: 14 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.

Lancaster's worst months

Month	US AQI	Days measured	World rank
August 2025	447.9 µg/m³	31 of 31	1,855thof 2,901
July 2024	437.7 µg/m³	27 of 31	1,459thof 2,566
May 2026	386.9 µg/m³	31 of 31	1,653rdof 2,874
September 2024	376.6 µg/m³	30 of 30	1,294thof 2,010
June 2025	356.3 µg/m³	30 of 30	2,128thof 2,508
June 2024	346.2 µg/m³	30 of 30	1,967thof 2,563

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.

Lancaster's worst days

Day	US AQI
27 Dec 2024	15561.2 µg/m³
16 May 2026	9432.3 µg/m³
7 Jan 2025	8024.9 µg/m³
17 May 2026	6818.0 µg/m³
28 Mar 2025	6717.5 µg/m³
13 Jul 2024	6617.1 µg/m³
16 Dec 2025	6617.0 µg/m³
20 Jan 2025	6616.9 µg/m³
4 Mar 2026	6516.6 µg/m³
17 Dec 2025	6416.1 µg/m³

Daily means, the highest since 11 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, Lancaster, United States, 11 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/lancaster/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.

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

Updated 2026-10-12 18:07 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).