SmogRank / United States / California / Gilroy
Gilroy, month by month
Gilroy has a measured daily mean on 1,157 days since 1 January 2023. Its worst month was December 2024, at 44 US AQI (8.0 µg/m³), 1,364th of 2,616 cities on that month's world ranking. Its cleanest was February 2024, at 14 US AQI (2.6 µg/m³). 2025 averaged 33 US AQI (5.9 µg/m³), against 27 US AQI (4.9 µg/m³) in 2023.
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
6 months
| Month | Why |
|---|---|
| Dec 2025 | 20 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks. |
| Nov 2025 | 14 of 30 days measured; a month needs 21. The others: 16 with under 18 hours of readings or readings that failed our checks. |
| Jun 2024 | 8 of 30 days measured; a month needs 21. The others: 22 with under 18 hours of readings or readings that failed our checks. |
| May 2024 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Apr 2024 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Mar 2024 | 18 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 12 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.
Gilroy's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| December 2024 | 448.0 µg/m³ | 1,364thof 2,616 | – |
| January 2025 | 448.0 µg/m³ | 1,406thof 2,474 | – |
| June 2025 | 448.0 µg/m³ | 1,834thof 2,508 | – |
| January 2026 | 427.6 µg/m³ | 1,617thof 2,617 | – |
| September 2023 | 407.2 µg/m³ | 1,431stof 2,176 | California and Oregon, United States, September 2023 |
| February 2023 | 376.7 µg/m³ | 957thof 1,129 | – |
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.
Gilroy's worst days
| Day | US AQI | Episode |
|---|---|---|
| 20 Sept 2023 | 11842.5 µg/m³ | California and Oregon, United States, September 2023 |
| 21 Sept 2023 | 8829.0 µg/m³ | California and Oregon, United States, September 2023 |
| 22 Sept 2023 | 8426.8 µg/m³ | California and Oregon, United States, September 2023 |
| 4 Jul 2026 | 7521.8 µg/m³ | – |
| 31 Aug 2023 | 7421.3 µg/m³ | – |
| 23 Sept 2023 | 6717.5 µg/m³ | California and Oregon, United States, September 2023 |
| 4 Jul 2024 | 6717.5 µg/m³ | – |
| 30 Aug 2023 | 6516.6 µg/m³ | – |
| 4 Jul 2023 | 6416.2 µg/m³ | – |
| 14 Dec 2025 | 6315.6 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, Gilroy, 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/gilroy/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.
Gilroy 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).