SmogRank / United States / California / La Mesa

La Mesa, month by month

La Mesa has a measured daily mean on one day since 14 February 2023.

Every month since 2023

2026too few days for a mean (a year needs 199)0 days measured
JannoneFebnoneMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnone
2025too few days for a mean (a year needs 256)0 days measured
JannoneFebnoneMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnoneNovnoneDecnone
2024too few days for a mean (a year needs 257)0 days measured
JannoneFebnoneMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnoneNovnoneDecnone
2023too few days for a mean (a year needs 256)1 day measured
JanFeb1 dayMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnoneNovnoneDecnone
Each square is a month's mean PM2.5 in US AQI from La Mesa'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 La Mesa marked; each year, the year's.
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

45 months
MonthWhy
Oct 2026No day measured.
Sep 2026No day measured.
Aug 2026No day measured.
Jul 2026No day measured.
Jun 2026No day measured.
May 2026No day measured.
Apr 2026No day measured.
Mar 2026No day measured.
Feb 2026No day measured.
Jan 2026No day measured.
Dec 2025No day measured.
Nov 2025No day measured.
Oct 2025No day measured.
Sep 2025No day measured.
Aug 2025No day measured.
Jul 2025No day measured.
Jun 2025No day measured.
May 2025No day measured.
Apr 2025No day measured.
Mar 2025No day measured.
Feb 2025No day measured.
Jan 2025No day measured.
Dec 2024No day measured.
Nov 2024No day measured.
Oct 2024No day measured.
Sep 2024No day measured.
Aug 2024No day measured.
Jul 2024No day measured.
Jun 2024No day measured.
May 2024No day measured.
Apr 2024No day measured.
Mar 2024No day measured.
Feb 2024No day measured.
Jan 2024No day measured.
Dec 2023No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Nov 2023No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Oct 2023No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Sep 2023No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Aug 2023No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jul 2023No day measured. The others: 1 missing from OpenAQ's archive, 30 with under 18 hours of readings or readings that failed our checks.
Jun 2023No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
May 2023No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Apr 2023No day measured. The others: 3 missing from OpenAQ's archive, 27 with under 18 hours of readings or readings that failed our checks.
Mar 2023No day measured. The others: 20 missing from OpenAQ's archive, 11 with under 18 hours of readings or readings that failed our checks.
Feb 20231 of 28 days measured; a month needs 20. The others: 13 missing from OpenAQ's archive, 1 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.

La Mesa's worst days

DayUS AQI
14 Feb 2023 376.7 µg/m³

Daily means, the highest since 14 Feb 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, La Mesa, United States, 14 Feb 2023 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/la-mesa/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.

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

Updated 2026-10-12 19:07 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).