SmogRank / United States / Colorado / Denver
Denver, month by month
Denver has a measured daily mean on 1,355 days since 1 January 2023. Its worst month was May 2023, at 58 US AQI (13.1 µg/m³), 207th of 1,600 cities on that month's world ranking. Its cleanest was May 2024, at 22 US AQI (3.9 µg/m³). 2025 averaged 36 US AQI (6.4 µg/m³), against 37 US AQI (6.6 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
1 month
| Month | Why |
|---|---|
| Dec 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. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Denver's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| May 2023 | 5813.1 µg/m³ | 207thof 1,600 | North-western United States and Canada, May 2023 |
| January 2023 | 5310.1 µg/m³ | 470thof 1,261 | – |
| October 2024 | 5310.1 µg/m³ | 513thof 2,020 | – |
| August 2026 | 529.9 µg/m³ | 917thof 2,896 | North-western United States and Canada, July and August 2026 |
| February 2025 | 519.3 µg/m³ | 1,296thof 2,633 | – |
| July 2024 | 519.2 µg/m³ | 951stof 2,566 | – |
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.
Denver's worst days
| Day | US AQI | Episode |
|---|---|---|
| 19 May 2023 | 17183.9 µg/m³ | North-western United States and Canada, May 2023 |
| 20 May 2023 | 15459.6 µg/m³ | North-western United States and Canada, May 2023 |
| 23 May 2023 | 9633.1 µg/m³ | North-western United States and Canada, May 2023 |
| 22 May 2023 | 9231.3 µg/m³ | North-western United States and Canada, May 2023 |
| 4 Aug 2026 | 8929.5 µg/m³ | North-western United States and Canada, July and August 2026 |
| 14 Dec 2023 | 8225.8 µg/m³ | – |
| 1 Oct 2024 | 8024.9 µg/m³ | – |
| 23 Jul 2024 | 8024.7 µg/m³ | – |
| 7 Aug 2026 | 7924.1 µg/m³ | – |
| 5 Aug 2026 | 7722.9 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, Denver, 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/denver/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.
Denver now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 18:07 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).