SmogRank / Canada / Ontario / Alliston
Alliston, month by month
Alliston has a measured daily mean on 692 days since 28 August 2024. Its worst month was July 2026, at 69 US AQI (18.7 µg/m³), 370th of 2,784 cities on that month's world ranking. Its cleanest was November 2024, at 18 US AQI (3.3 µg/m³).
Every month since 2024
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
3 months
| Month | Why |
|---|---|
| Nov 2025 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Oct 2025 | 10 of 31 days measured; a month needs 22. The others: 21 with under 18 hours of readings or readings that failed our checks. |
| Aug 2024 | 4 of 31 days measured; a month needs 22. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Alliston's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2026 | 6918.7 µg/m³ | 370thof 2,784 | Northern United States and Canada, July 2026 |
| July 2025 | 5812.7 µg/m³ | 702ndof 2,889 | North-eastern United States and Canada, 29 July to 9 August 2025 Northern United States and Canada, July 2025 |
| August 2025 | 5812.7 µg/m³ | 633rdof 2,901 | North-eastern United States and Canada, 29 July to 9 August 2025 |
| June 2025 | 5611.8 µg/m³ | 844thof 2,508 | Northern United States and Canada, May and June 2025 |
| February 2026 | 468.2 µg/m³ | 1,912thof 2,866 | North-eastern United States and Canada, 14 to 19 February 2026 |
| March 2026 | 376.6 µg/m³ | 2,441stof 2,971 | North-eastern United States and Canada, March 2026 |
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.
Alliston's worst days
Daily means, the highest since 28 Aug 2024; 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, Alliston, Canada, 28 Aug 2024 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/ca/alliston/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.
Alliston 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).