SmogRank / United States / California / Willows
Willows, month by month
Willows has a measured daily mean on 1,252 days since 1 January 2023. Its worst month was August 2023, at 53 US AQI (10.4 µg/m³), 552nd of 1,980 cities on that month's world ranking. Its cleanest was March 2024, at 15 US AQI (2.7 µg/m³). 2025 averaged 37 US AQI (6.7 µg/m³), against 31 US AQI (5.6 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
4 months
| Month | Why |
|---|---|
| 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 | 18 of 31 days measured; a month needs 22. The others: 6 with no readings from the monitor, 7 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.
Willows's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| August 2023 | 5310.4 µg/m³ | 552ndof 1,980 | North-western United States and Canada, August 2023 |
| July 2023 | 529.6 µg/m³ | 700thof 1,432 | – |
| September 2025 | 509.0 µg/m³ | 897thof 3,104 | – |
| July 2025 | 488.7 µg/m³ | 1,588thof 2,889 | – |
| October 2024 | 468.2 µg/m³ | 771stof 2,020 | – |
| September 2023 | 458.1 µg/m³ | 1,077thof 2,176 | – |
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.
Willows's worst days
| Day | US AQI | Episode |
|---|---|---|
| 7 Oct 2025 | 11440.8 µg/m³ | – |
| 30 Aug 2023 | 9331.5 µg/m³ | North-western United States and Canada, August 2023 |
| 10 Jul 2025 | 9130.4 µg/m³ | – |
| 11 Jul 2025 | 8628.0 µg/m³ | – |
| 24 Oct 2025 | 8527.2 µg/m³ | – |
| 22 Nov 2023 | 8024.6 µg/m³ | – |
| 29 Aug 2023 | 7924.0 µg/m³ | North-western United States and Canada, August 2023 |
| 31 Aug 2023 | 7421.3 µg/m³ | North-western United States and Canada, August 2023 |
| 30 Jan 2025 | 7421.2 µg/m³ | – |
| 22 Sept 2023 | 7220.6 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, Willows, 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/willows/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.
Willows now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 17:07 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).