SmogRank / United States / California / Vacaville
Vacaville, month by month
Vacaville has a measured daily mean on 1,267 days since 1 January 2023. Its worst month was January 2026, at 53 US AQI (10.1 µg/m³), 1,094th of 2,617 cities on that month's world ranking. Its cleanest was March 2024, at 13 US AQI (2.4 µg/m³). 2025 averaged 32 US AQI (5.7 µg/m³), against 26 US AQI (4.6 µg/m³) in 2024.
Every month since 2023
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
2 months
| Month | Why |
|---|---|
| Mar 2023 | 11 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive. |
| Feb 2023 | 1 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.
Vacaville's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| January 2026 | 5310.1 µg/m³ | 1,094thof 2,617 | – |
| December 2024 | 529.8 µg/m³ | 908thof 2,616 | California and Oregon, United States, December 2024 |
| January 2025 | 488.7 µg/m³ | 1,245thof 2,474 | – |
| December 2025 | 478.4 µg/m³ | 1,734thof 3,006 | – |
| November 2025 | 458.1 µg/m³ | 1,509thof 2,715 | – |
| December 2023 | 386.8 µg/m³ | 1,618thof 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.
Vacaville's worst days
| Day | US AQI | Episode |
|---|---|---|
| 22 Sept 2023 | 8426.8 µg/m³ | California and Oregon, United States, September 2023 |
| 11 Dec 2024 | 8426.8 µg/m³ | California and Oregon, United States, December 2024 |
| 20 Sept 2023 | 8326.3 µg/m³ | California and Oregon, United States, September 2023 |
| 7 Dec 2024 | 8024.8 µg/m³ | California and Oregon, United States, December 2024 |
| 17 Jan 2026 | 8024.8 µg/m³ | – |
| 31 Aug 2023 | 7823.8 µg/m³ | – |
| 4 Dec 2025 | 7723.3 µg/m³ | – |
| 21 Sept 2023 | 7421.7 µg/m³ | California and Oregon, United States, September 2023 |
| 5 Dec 2025 | 7421.3 µg/m³ | – |
| 16 Jan 2026 | 7119.8 µg/m³ | – |
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, Vacaville, United States, 1 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/vacaville/history (accessed 12 Oct 2026).
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.
Vacaville now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 23:07 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).