SmogRank / United States / Oregon / Altamont
Altamont, month by month
Altamont has a measured daily mean on 1,352 days since 1 January 2023. Its worst month was August 2023, at 75 US AQI (21.8 µg/m³), 111th of 1,980 cities on that month's world ranking. Its cleanest was June 2024, at 16 US AQI (2.9 µg/m³). 2025 averaged 41 US AQI (7.4 µg/m³), against 43 US AQI (7.7 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
1 month
| Month | Why |
|---|---|
| Oct 2026 | 7 of 11 days measured; a month needs 8. The others: 2 with no readings from the monitor, 2 with readings for part of the day (a day needs 18 hours). |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Altamont's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| August 2023 | 7521.8 µg/m³ | 111thof 1,980 | North-western United States and Canada, August 2023 |
| August 2024 | 6918.9 µg/m³ | 109thof 2,010 | Oregon, Idaho and Utah, United States, August 2024 North-western United States and Canada, August 2024 |
| November 2023 | 6416.0 µg/m³ | 129thof 2,243 | North-western United States and Canada, October and November 2023 |
| July 2024 | 6315.8 µg/m³ | 161stof 2,566 | North-western United States and Canada, July 2024 |
| November 2025 | 5913.4 µg/m³ | 656thof 2,715 | – |
| January 2025 | 5813.0 µg/m³ | 614thof 2,474 | – |
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.
Altamont's worst days
| Day | US AQI | Episode |
|---|---|---|
| 9 Aug 2024 | 17082.4 µg/m³ | Oregon, Idaho and Utah, United States, August 2024 |
| 10 Aug 2026 | 15764.0 µg/m³ | North-western United States and Canada, 4 to 22 August 2026 |
| 28 Aug 2023 | 15663.2 µg/m³ | North-western United States and Canada, August 2023 |
| 18 Jul 2026 | 15662.2 µg/m³ | North-western United States and Canada, July and August 2026 |
| 11 Aug 2024 | 15561.2 µg/m³ | – |
| 29 Aug 2023 | 15560.8 µg/m³ | North-western United States and Canada, August 2023 |
| 1 Aug 2024 | 15358.8 µg/m³ | North-western United States and Canada, August 2024 |
| 23 Aug 2023 | 15358.6 µg/m³ | North-western United States and Canada, August 2023 |
| 17 Jul 2026 | 15358.2 µg/m³ | North-western United States and Canada, July and August 2026 |
| 16 Jul 2025 | 14754.2 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, Altamont, 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/altamont/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.
Altamont now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 22:07 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).