Castlegar vs St. Catharines: PM2.5 compared

Over the last year, Castlegar's air was about 1.6× as polluted as St. Catharines's: PM2.5 averaged 11.0 µg/m³ against 6.8, on the 323 days both cities were measured. Castlegar had the dirtier air on 211 of those days, St. Catharines on 111. Castlegar was over the WHO's daily guideline of 15 µg/m³ on 39 of them, St. Catharines on 15.

Right now

Castlegar#770on the 24-hour board of 2,002, at 45 US AQI (8.1 µg/m³)

St. Catharines#1,855on the 24-hour board of 2,002, at 15 US AQI (2.7 µg/m³)

The last year, day by day

Castlegar

St. Catharines

Each city's daily mean from 7 Oct 2025 to 6 Oct 2026, one stripe a day, coloured by band. A blank stripe is a day without a daily mean.

Month by month

Monthly means in µg/m³ over the days both cities were measured. Solid: Castlegar. Faded: St. Catharines. A month shows once both share 10 such days. Dashed line: the WHO daily guideline, 15 µg/m³.

Year by year

Year	Castlegar	St. Catharines	Days both measured	Days Castlegar was worse
2026 so far	57	41	246	156
2025	42	39	343	186
2024	39	35	344	181
2023	54	53	278	126

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. Catharines

17 Jul 2026187107.0 µg/m³
16 Jul 2026186106.0 µg/m³
18 Jul 202614352.6 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. Catharines

Side by side with Buffalo (the nearest), Gujranwala (the world's worst on 30 days).

Use this page

SmogRank, PM2.5 daily means compared, Castlegar and St. Catharines, 7 Oct 2025 – 6 Oct 2026, smogrank.com/compare/ca-castlegar/ca-st-catharines (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.