Markham Seasonal Pollution
Markham usually records its highest OpenAQ-derived EPA AQI in September and its cleanest month in November. The page uses OpenAQ-derived daily history for 1 mapped monitoring location in Ontario, Canada.
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Average EPA AQI
45
Rank 7 of 158 cities by average AQI
PM2.5
11.2
ug/m3 annualized city average
Seasonality
September
Cleanest: November
Health indicator
0.5
cigarette-equivalent per day
Yearly EPA AQI trend
Seasonal EPA AQI heatmap
JanFebMarAprMayJunJulAugSepOctNovDec
Markham
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59
42
34
51
What this seasonality page measures
Find each city's worst and cleanest months from daily OpenAQ-derived EPA AQI.
For Markham, the current global analytics build covers 112 daily rows from 2024-09-12 to 2025-01-01. The calculations normalize PM2.5 and PM10 observations into US EPA AQI bands so country, city, and tool pages use one consistent method.