SmogRank / United States / California / Alta Sierra
Alta Sierra, month by month
Alta Sierra has a measured daily mean on 1,313 days since 1 January 2023. Its worst month was July 2026, at 53 US AQI (10.2 µg/m³), 1,303rd of 2,784 cities on that month's world ranking. Its cleanest was October 2024, at 19 US AQI (3.4 µg/m³). 2025 averaged 34 US AQI (6.2 µg/m³), against 27 US AQI (4.9 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: 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.
Alta Sierra's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2026 | 5310.2 µg/m³ | 1,303rdof 2,784 | – |
| June 2026 | 529.7 µg/m³ | 699thof 2,497 | – |
| August 2026 | 529.6 µg/m³ | 997thof 2,896 | North-western United States and Canada, 4 to 22 August 2026 |
| December 2025 | 529.4 µg/m³ | 1,490thof 3,006 | – |
| November 2025 | 519.3 µg/m³ | 1,182ndof 2,715 | – |
| May 2026 | 519.2 µg/m³ | 957thof 2,874 | – |
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.
Alta Sierra's worst days
| Day | US AQI | Episode |
|---|---|---|
| 2 Jul 2026 | 11741.8 µg/m³ | – |
| 17 Feb 2026 | 9029.9 µg/m³ | – |
| 5 Aug 2026 | 8527.6 µg/m³ | North-western United States and Canada, 4 to 22 August 2026 |
| 6 Aug 2026 | 8024.9 µg/m³ | North-western United States and Canada, 4 to 22 August 2026 |
| 1 Aug 2024 | 7622.7 µg/m³ | – |
| 25 Feb 2025 | 7421.6 µg/m³ | – |
| 9 Aug 2024 | 7119.8 µg/m³ | – |
| 31 Aug 2026 | 6918.7 µg/m³ | – |
| 12 Jul 2025 | 6818.3 µg/m³ | – |
| 31 Jul 2024 | 6818.0 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, Alta Sierra, 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/alta-sierra-california/history (accessed 13 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.
Alta Sierra now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-13 02:07 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).