SmogRank / United States / California / Colusa
Colusa, month by month
Colusa has a measured daily mean on 1,248 days since 1 January 2023. Its worst month was August 2023, at 54 US AQI (10.7 µg/m³), 487th of 1,980 cities on that month's world ranking. Its cleanest was March 2024, at 16 US AQI (2.9 µg/m³). 2025 averaged 36 US AQI (6.5 µg/m³), against 34 US AQI (6.1 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
5 months
| Month | Why |
|---|---|
| Jan 2026 | 21 of 31 days measured; a month needs 22. The others: 5 with no readings from the monitor, 5 with readings for part of the day (a day needs 18 hours). |
| Nov 2025 | 18 of 30 days measured; a month needs 21. The others: 3 with no readings from the monitor, 9 with readings for part of the day (a day needs 18 hours). |
| Dec 2024 | 19 of 31 days measured; a month needs 22. The others: 6 with no readings from the monitor, 6 with readings for part of the day (a day needs 18 hours). |
| Mar 2023 | 10 of 31 days measured; a month needs 22. The others: 1 with readings for part of the day (a day needs 18 hours), 20 missing from OpenAQ's archive. |
| Feb 2023 | 1 of 28 days measured; a month needs 20. The others: 2 with readings for part of the day (a day needs 18 hours), 25 missing from OpenAQ's archive. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Colusa's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| August 2023 | 5410.7 µg/m³ | 487thof 1,980 | North-western United States and Canada, August 2023 |
| July 2023 | 5410.5 µg/m³ | 600thof 1,432 | – |
| September 2023 | 5310.1 µg/m³ | 579thof 2,176 | California and Oregon, United States, September 2023 |
| November 2023 | 529.8 µg/m³ | 668thof 2,243 | – |
| October 2023 | 509.0 µg/m³ | 488thof 2,012 | – |
| July 2024 | 498.9 µg/m³ | 1,046thof 2,566 | – |
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.
Colusa's worst days
| Day | US AQI | Episode |
|---|---|---|
| 30 Aug 2023 | 9733.7 µg/m³ | North-western United States and Canada, August 2023 |
| 5 Jul 2024 | 9231.0 µg/m³ | – |
| 20 Sept 2023 | 8829.0 µg/m³ | California and Oregon, United States, September 2023 |
| 22 Sept 2023 | 8628.1 µg/m³ | California and Oregon, United States, September 2023 |
| 30 Nov 2023 | 8225.9 µg/m³ | – |
| 29 Jan 2025 | 8125.0 µg/m³ | Western United States and Mexico, January and February 2025 |
| 2 Aug 2024 | 7923.9 µg/m³ | – |
| 30 Jan 2025 | 7923.9 µg/m³ | Western United States and Mexico, January and February 2025 |
| 31 Aug 2023 | 7823.5 µg/m³ | North-western United States and Canada, August 2023 |
| 10 Jul 2025 | 7723.3 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, Colusa, 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/colusa/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.
Colusa 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).