SmogRank / Castlegar / St. Thomas
Castlegar vs St. Thomas: PM2.5 compared
Over the last year, Castlegar's air was 34% more polluted than St. Thomas's: PM2.5 averaged 11.1 µg/m³ against 8.3, on the 317 days both cities were measured. Castlegar had the dirtier air on 200 of those days, St. Thomas on 112. Castlegar was over the WHO's daily guideline of 15 µg/m³ on 39 of them, St. Thomas on 22.
Right now
The last year, day by day
Month by month
Year by year
| Year | Castlegar | St. Thomas | Days Castlegar was worse |
|---|---|---|---|
| 2026 so far | 57 | 52 | 147 |
| 2025 | 42 | 40 | 183 |
| 2024 | 41 | 37 | 158 |
| 2023 | 54 | 54 | 124 |
Means in US AQI over the days both cities were measured that year; a year shows once they share 30 such days.
Each city's worst days
Castlegar
- 11 Aug 2026227152.0 µg/m³
- 9 Aug 2026193116.0 µg/m³
- 7 Aug 2026187107.0 µg/m³
St. Thomas
- 16 Jul 2026368259.0 µg/m³
- 17 Jul 2026344247.0 µg/m³
- 15 Jul 202616271.1 µg/m³
Daily means in US AQI, with µg/m³ beside them, since the index stops at its top value, over the days both cities were measured in the last year. Each date opens that day's world board.
Compare either city with another
Castlegar
Side by side with Creston (the nearest), Edmonton (Canada's 2nd worst on 30 days), Gujranwala (the world's worst on 30 days).
St. Thomas
Side by side with London (the nearest), Gujranwala (the world's worst on 30 days).
Use this page
SmogRank, PM2.5 daily means compared, Castlegar and St. Thomas, 7 Oct 2025 – 6 Oct 2026, smogrank.com/compare/ca-castlegar/ca-st-thomas (accessed 7 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.
The same rules as every SmogRank figure: reference monitors first, and a day counts with 18 measured hours. How we measure.
Updated 2026-10-07 08:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.