Helsinki Seasonal Pollution
Helsinki usually records its highest OpenAQ-derived EPA AQI in May and its cleanest month in December. The page uses OpenAQ-derived daily history for 3 mapped monitoring locations in Uusimaa, Finland.
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Average EPA AQI
31
Rank 1 of 22 cities by average AQI
PM2.5
5.8
ug/m3 annualized city average
Seasonality
May
Cleanest: December
Health indicator
0.3
cigarette-equivalent per day
Yearly EPA AQI trend
Seasonal EPA AQI heatmap
JanFebMarAprMayJunJulAugSepOctNovDec
Helsinki
31
31
40
31
41
33
33
32
37
24
21
19
What this seasonality page measures
Find each city's worst and cleanest months from daily OpenAQ-derived EPA AQI.
For Helsinki, the current global analytics build covers 350 daily rows from 2024-01-01 to 2024-12-31. The calculations normalize PM2.5 and PM10 observations into US EPA AQI bands so country, city, and tool pages use one consistent method.