Hillsborough County, New Hampshire

AQI 38 · Good

YearMonth

38

Median AQI

56

90th Percentile

123

Max AQI

274

Days with Data

Ranked #4 of 7 counties in New Hampshire (by median AQI, lower is better)

Monthly Median AQI — 2025

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AQI Category Breakdown

Adjacent Counties

Essex County, Massachusetts Middlesex County, Massachusetts Worcester County, Massachusetts Cheshire County Merrimack County Rockingham County Sullivan County

External Links

Hillsborough County, New Hampshire on Wikipedia