Mason County, Washington
AQI 21 · Good21
Median AQI
41
90th Percentile
67
Max AQI
243
Days with Data
Ranked #11 of 31 counties in Washington (by median AQI, lower is better)
Monthly Median AQI — 2025
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21
Median AQI
41
90th Percentile
67
Max AQI
243
Days with Data
Ranked #11 of 31 counties in Washington (by median AQI, lower is better)
Click a bar to view that month's details