Counties in New Hampshire by highest daily Air Quality Index (US EPA)

Hillsborough County had the highest highest daily Air Quality Index (US EPA) of 10 counties in 1996, at 168. Belknap County had the lowest, at 126. The median was 154. Source: the U.S. Environmental Protection Agency.

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Median15410 counties

Map of counties, 1996

Belknap County: 126 indexCarroll County: 136 indexCheshire County: 161 indexCoos County: 129 indexGrafton County: 151 indexHillsborough County: 168 indexMerrimack County: 156 indexRockingham County: 161 indexStrafford County: 159 indexSullivan County: 151 index
  • Under 130
  • 130 to 150
  • 150 to 160
  • 160 and over
index, 1996. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 1996

Hillsborough County: 168 indexHillsborough County168Cheshire County: 161 indexCheshire County161Rockingham County: 161 indexRockingham County161Strafford County: 159 indexStrafford County159Merrimack County: 156 indexMerrimack County156Grafton County: 151 indexGrafton County151Sullivan County: 151 indexSullivan County151Carroll County: 136 indexCarroll County136Coos County: 129 indexCoos County129Belknap County: 126 indexBelknap County126Hillsborough County: 168 indexHillsborough County168Cheshire County: 161 indexCheshire County161Rockingham County: 161 indexRockingham County161Strafford County: 159 indexStrafford County159Merrimack County: 156 indexMerrimack County156Grafton County: 151 indexGrafton County151Sullivan County: 151 indexSullivan County151Carroll County: 136 indexCarroll County136Coos County: 129 indexCoos County129Belknap County: 126 indexBelknap County126
index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties1996
index
Change on 1995
1Hillsborough County168-19
2Cheshire County161+49
2Rockingham County161-39
4Strafford County159+115
5Merrimack County156+51
6Grafton County151+50
6Sullivan County151+25
8Carroll County136n/a
9Coos County129-14
10Belknap County126n/a

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. Equal values share a rank.

How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: highest daily AQI (Counties in New Hampshire by highest daily Air Quality Index (US EPA), 1996) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: highest daily AQI, Counties in New Hampshire by highest daily Air Quality Index (US EPA), 1996. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/new-hampshire-counties?period=1996. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in New Hampshire by highest daily Air Quality Index (US EPA), 1996. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/new-hampshire-counties?period=1996.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in New Hampshire by highest daily Air Quality Index (US EPA), 1996 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/new-hampshire-counties?period=1996 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_new_hampshire_1996,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Counties in New Hampshire by highest daily Air Quality Index (US EPA), 1996}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/new-hampshire-counties?period=1996. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download\_files.html\#Annual. Retrieved 2026-10-12.},
}
RIS
TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: highest daily AQI: Counties in New Hampshire by highest daily Air Quality Index (US EPA), 1996
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/highest-daily-air-quality-index/new-hampshire-counties?period=1996
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/new-hampshire-counties?period=1996.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  - 
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Rank Counties in New Hampshire by highest daily Air Quality Index (US EPA) using official data, and cite the source.
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Questions

Which county has the highest highest daily Air Quality Index (US EPA)?

Hillsborough County, with 168 in 1996, according to the U.S. Environmental Protection Agency.

Which county has the lowest highest daily Air Quality Index (US EPA)?

Belknap County, with 126 in 1996.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Highest daily Air Quality Index (US EPA): other rankings

Counties in New Hampshire: more rankings