SmogRank / United States / Maine / Lewiston
Lewiston, month by month
Lewiston has a measured daily mean on 1,318 days since 1 January 2023. Its worst month was July 2025, at 52 US AQI (9.4 µg/m³), 1,423rd of 2,889 cities on that month's world ranking. Its cleanest was April 2023, at 13 US AQI (2.4 µg/m³). 2025 averaged 31 US AQI (5.5 µg/m³), against 26 US AQI (4.6 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 |
|---|---|
| Jun 2023 | 20 of 30 days measured; a month needs 21. The others: 10 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.
Lewiston's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2025 | 529.4 µg/m³ | 1,423rdof 2,889 | North-eastern United States and Canada, 29 July to 9 August 2025 North-eastern United States and Canada, 24 to 28 July 2025 |
| July 2023 | 519.3 µg/m³ | 729thof 1,432 | – |
| August 2025 | 478.5 µg/m³ | 1,639thof 2,901 | North-eastern United States and Canada, 29 July to 9 August 2025 |
| September 2023 | 468.3 µg/m³ | 1,008thof 2,176 | – |
| July 2026 | 468.3 µg/m³ | 1,796thof 2,784 | – |
| June 2025 | 448.0 µg/m³ | 1,834thof 2,508 | – |
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.
Lewiston's worst days
| Day | US AQI | Episode |
|---|---|---|
| 26 Jul 2025 | 10738.0 µg/m³ | North-eastern United States and Canada, 24 to 28 July 2025 |
| 4 Aug 2025 | 9432.2 µg/m³ | North-eastern United States and Canada, 29 July to 9 August 2025 |
| 8 Jun 2025 | 7923.9 µg/m³ | – |
| 31 Jul 2025 | 7823.5 µg/m³ | North-eastern United States and Canada, 29 July to 9 August 2025 |
| 6 Sept 2023 | 7522.1 µg/m³ | – |
| 1 Oct 2023 | 7522.0 µg/m³ | – |
| 18 Jul 2023 | 7421.7 µg/m³ | – |
| 7 Sept 2023 | 7320.8 µg/m³ | – |
| 30 Sept 2023 | 7119.7 µg/m³ | – |
| 7 Aug 2023 | 7019.3 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, Lewiston, 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/lewiston/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.
Lewiston now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 20:07 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).