SmogRank / United States / California / Vallejo

Vallejo, month by month

Vallejo has a measured daily mean on 766 days since 11 January 2023. Its worst month was December 2024, at 59 US AQI (13.6 µg/m³), 551st of 2,616 cities on that month's world ranking. Its cleanest was April 2026, at 21 US AQI (3.7 µg/m³).

Every month since 2023

202639 so far262 days measured2,217th of 2,791 in the world
Jan57#911Feb38#2,253Mar33#2,553Apr21#2,780May27#2,385Jun46#1,010Jul36#2,293Aug37#2,249Sep37#1,442Oct44#1,027
202539 for the year320 days measured2,057th of 2,681 in the world
Jan54#848Feb30#2,286Mar25#2,567Apr20 daysMay42#1,478Jun43#1,890Jul28#2,595Aug36#2,366Sep41#1,562Oct39#1,173Nov15 daysDec40#2,090
2024too few days for a mean (a year needs 257)128 days measured
JannoneFeb1 dayMar1 dayAprnoneMaynoneJun2 daysJul13 daysAug13 daysSep29#1,697Oct41#1,000Nov20 daysDec59#551
2023too few days for a mean (a year needs 256)56 days measured
Jan7 daysFeb44#822Mar20 daysApr3 daysMaynoneJunnoneJul1 dayAugnoneSepnoneOctnoneNovnoneDecnone
Each square is a month's mean PM2.5 in US AQI from Vallejo'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 Vallejo 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

22 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.
Apr 202520 of 30 days measured; a month needs 21. The others: 10 with under 18 hours of readings or readings that failed our checks.
Nov 202420 of 30 days measured; a month needs 21. The others: 10 with under 18 hours of readings or readings that failed our checks.
Aug 202413 of 31 days measured; a month needs 22. The others: 18 with under 18 hours of readings or readings that failed our checks.
Jul 202413 of 31 days measured; a month needs 22. The others: 18 with under 18 hours of readings or readings that failed our checks.
Jun 20242 of 30 days measured; a month needs 21. The others: 28 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 20241 of 31 days measured; a month needs 22. The others: 30 with under 18 hours of readings or readings that failed our checks.
Feb 20241 of 29 days measured; a month needs 21. The others: 28 with under 18 hours of readings or readings that failed our checks.
Jan 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
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 20231 of 31 days measured; a month needs 22. The others: 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 20233 of 30 days measured; a month needs 21. The others: 27 with under 18 hours of readings or readings that failed our checks.
Mar 202320 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks.
Jan 20237 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.

Vallejo's worst months

MonthUS AQIDays measuredWorld rankEpisode
December 2024 5913.6 µg/m³25 of 31551stof 2,616South-western United States and Mexico, December 2024 to January 2025
California and Oregon, United States, December 2024
January 2026 5712.3 µg/m³29 of 31911thof 2,617California and Oregon, United States, January 2026
January 2025 5410.9 µg/m³31 of 31848thof 2,474South-western United States and Mexico, December 2024 to January 2025
June 2026 468.2 µg/m³30 of 301,010thof 2,497–
February 2023 448.0 µg/m³25 of 28822ndof 1,129–
June 2025 437.7 µg/m³27 of 301,890thof 2,508–

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.

Vallejo's worst days

DayUS AQIEpisode
7 Dec 2024 10637.6 µg/m³California and Oregon, United States, December 2024
1 Jan 2025 8828.7 µg/m³South-western United States and Mexico, December 2024 to January 2025
8 Dec 2024 8628.0 µg/m³California and Oregon, United States, December 2024
11 Dec 2024 8326.3 µg/m³California and Oregon, United States, December 2024
15 Jan 2026 8125.1 µg/m³California and Oregon, United States, January 2026
14 Jan 2026 7723.1 µg/m³California and Oregon, United States, January 2026
4 Dec 2024 7622.5 µg/m³California and Oregon, United States, December 2024
17 Jan 2026 7521.9 µg/m³California and Oregon, United States, January 2026
16 Jan 2026 7320.8 µg/m³California and Oregon, United States, January 2026
4 Feb 2026 7220.5 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, Vallejo, 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/vallejo/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.

Vallejo 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).