SmogRank / United States / California / Simi Valley
Simi Valley, month by month
Simi Valley has a measured daily mean on 1,310 days since 11 January 2023. Its worst month was May 2024, at 55 US AQI (11.1 µg/m³), 585th of 2,684 cities on that month's world ranking. Its cleanest was February 2023, at 21 US AQI (3.8 µg/m³). 2025 averaged 42 US AQI (7.6 µg/m³), against 42 US AQI (7.5 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
3 months
| Month | Why |
|---|---|
| Apr 2023 | 18 of 30 days measured; a month needs 21. The others: 12 with under 18 hours of readings or readings that failed our checks. |
| Mar 2023 | 20 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks. |
| Jan 2023 | 6 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 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.
Simi Valley's worst months
| Month | US AQI | World rank |
|---|---|---|
| May 2024 | 5511.1 µg/m³ | 585thof 2,684 |
| August 2025 | 5410.7 µg/m³ | 1,069thof 2,901 |
| July 2023 | 5310.4 µg/m³ | 619thof 1,432 |
| June 2025 | 5310.1 µg/m³ | 1,264thof 2,508 |
| July 2026 | 5310.0 µg/m³ | 1,357thof 2,784 |
| September 2023 | 529.9 µg/m³ | 607thof 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.
Simi Valley's worst days
| Day | US AQI |
|---|---|
| 16 Jun 2024 | 8929.3 µg/m³ |
| 4 Jul 2026 | 7924.1 µg/m³ |
| 23 Dec 2025 | 7722.8 µg/m³ |
| 4 Dec 2024 | 7421.4 µg/m³ |
| 23 Sept 2023 | 7120.1 µg/m³ |
| 20 Dec 2025 | 6918.7 µg/m³ |
| 13 May 2024 | 6818.4 µg/m³ |
| 24 Sept 2023 | 6818.3 µg/m³ |
| 5 Aug 2025 | 6818.2 µg/m³ |
| 21 Sept 2023 | 6818.1 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, Simi Valley, 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/simi-valley/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.
Simi Valley 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).