SmogRank / United States / Wyoming / Casper
Casper, month by month
Casper has a measured daily mean on 1,329 days since 2 January 2023. Its worst month was August 2026, at 47 US AQI (8.5 µg/m³), 1,373rd of 2,896 cities on that month's world ranking. Its cleanest was January 2026, at 5 US AQI (0.9 µg/m³). 2025 averaged 20 US AQI (3.6 µg/m³), against 24 US AQI (4.3 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 |
|---|---|
| Nov 2025 | 19 of 30 days measured; a month needs 21. 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.
Casper's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| August 2026 | 478.5 µg/m³ | 1,373rdof 2,896 | North-western United States and Canada, July and August 2026 |
| July 2024 | 468.2 µg/m³ | 1,275thof 2,566 | North-western United States and Canada, July 2024 |
| October 2024 | 397.1 µg/m³ | 1,080thof 2,020 | – |
| August 2024 | 376.7 µg/m³ | 1,615thof 2,010 | – |
| May 2023 | 336.0 µg/m³ | 1,297thof 1,600 | North-western United States and Canada, May 2023 Northern United States and Canada, May 2023 |
| July 2025 | 336.0 µg/m³ | 2,304thof 2,889 | – |
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.
Casper's worst days
| Day | US AQI | Episode |
|---|---|---|
| 22 Aug 2024 | 14553.4 µg/m³ | – |
| 19 May 2023 | 10436.7 µg/m³ | North-western United States and Canada, May 2023 Northern United States and Canada, May 2023 |
| 18 May 2023 | 9532.7 µg/m³ | Northern United States and Canada, May 2023 |
| 3 Aug 2026 | 8829.0 µg/m³ | North-western United States and Canada, July and August 2026 |
| 5 Sept 2023 | 8426.8 µg/m³ | Northern United States and Canada, August and September 2023 |
| 23 Jul 2024 | 8226.0 µg/m³ | North-western United States and Canada, July 2024 |
| 6 Oct 2024 | 7823.5 µg/m³ | – |
| 4 Sept 2025 | 7722.9 µg/m³ | – |
| 4 Aug 2026 | 7522.0 µg/m³ | North-western United States and Canada, July and August 2026 |
| 8 Aug 2026 | 7320.8 µg/m³ | – |
Daily means, the highest since 2 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, Casper, United States, 2 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/casper/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.
Casper 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).