SmogRank / United States / California / Concord

Concord, month by month

Concord has a measured daily mean on 1,091 days since 1 January 2023. Its worst month was December 2024, at 52 US AQI (9.4 µg/m³), 982nd of 2,616 cities on that month's world ranking. Its cleanest was February 2025, at 16 US AQI (2.9 µg/m³). 2025 averaged 26 US AQI (4.6 µg/m³), against 36 US AQI (6.5 µg/m³) in 2023.

Every month since 2023

202632 so far263 days measured2,917th of 3,214 in the world
Jan45#1,738Feb30#2,831Mar28#2,975Apr22#3,095May25#2,862Jun29#2,720Jul32#2,693Aug36#2,494Sep34#1,858Oct42#1,568
202526 for the year336 days measured2,829th of 2,926 in the world
Jan36#2,111Feb16#2,829Mar20#2,954Apr23#2,955May24#2,787Jun29#2,859Jul22#2,956Aug22#3,014Sep24#2,939Oct21#2,841Nov16 daysDec42#2,140
2024too few days for a mean (a year needs 257)192 days measured
Jan25#2,178Feb22#2,323MarnoneAprnoneMaynoneJunnoneJul8 daysAug16#2,003Sep17#1,987Oct16#1,998Nov19#2,534Dec52#982
202336 for the year300 days measured1,118th of 1,355 in the world
Jan31#1,037Feb1 dayMar10 daysApr28#1,342May29#1,398Jun30#1,385Jul45#845Aug45#985Sep45#1,077Oct27#1,806Nov38#1,493Dec44#1,260
Each square is a month's mean PM2.5 in US AQI from Concord'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 Concord marked; each year, the year's. A dashed square is the running month, so far.
Good0–50
Moderate51–100
Unhealthy for 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

8 months
MonthWhy
Nov 202516 of 30 days measured; a month needs 21. The others: 8 with no readings from the monitor, 6 with readings for part of the day (a day needs 18 hours).
Jul 20248 of 31 days measured; a month needs 22. The others: 23 with under 18 hours of readings or readings that failed our checks.
Jun 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
May 2024No day measured. The others: 31 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 202310 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive, 1 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.

Concord's worst months

MonthUS AQIDays measuredWorld rankEpisode
December 2024 529.4 µg/m³24 of 31982ndof 2,616California and Oregon, United States, December 2024
July 2023 458.1 µg/m³29 of 31845thof 1,432–
August 2023 458.1 µg/m³31 of 31985thof 1,980–
September 2023 458.1 µg/m³30 of 301,077thof 2,176California and Oregon, United States, September 2023
January 2026 458.1 µg/m³31 of 311,738thof 2,978–
December 2023 448.0 µg/m³30 of 311,260thof 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.

Concord's worst days

DayUS AQIEpisode
20 Sept 2023 11039.3 µg/m³California and Oregon, United States, September 2023
22 Sept 2023 9029.9 µg/m³California and Oregon, United States, September 2023
21 Sept 2023 8929.5 µg/m³California and Oregon, United States, September 2023
7 Dec 2024 8326.5 µg/m³California and Oregon, United States, December 2024
11 Dec 2024 8125.4 µg/m³California and Oregon, United States, December 2024
31 Aug 2023 7823.7 µg/m³–
23 Sept 2023 7320.8 µg/m³California and Oregon, United States, September 2023
30 Aug 2023 7119.9 µg/m³–
10 Dec 2024 6918.8 µg/m³California and Oregon, United States, December 2024
19 Sept 2023 6818.1 µg/m³California and Oregon, United States, September 2023

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, Concord, United States, 1 Jan 2023 – 12 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/concord/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.

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

Updated 2026-10-13 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).