Data / Median Air Quality Index (US EPA) / Merrimack County

Median Air Quality Index (US EPA) in Merrimack County

Median Air Quality Index (US EPA) in Merrimack County was 37 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged from 2024.

2025, index37
Change on 20240
Series high452005
Series low191991

Next release: Tuesday, 13 July 2027, estimated by Invokely from past publication dates (low confidence), not announced by the publisher. Release calendar

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Median Air Quality Index (US EPA) in Merrimack County, 1985 to 2025

102030405019851991199720032009201520251985: 25 index1986: 33 index1987: 28 index1988: 40 index1989: 43 index1990: 41 index1991: 19 index1992: 30 index1993: 29 index1994: 28 index1995: 29 index1996: 31 index1997: 32 index1998: 32 index1999: 39 index2000: 32 index2001: 39 index2002: 39 index2003: 39 index2004: 41 index2005: 45 index2006: 40 index2007: 40 index2008: 41 index2009: 36 index2010: 40 index2011: 38 index2012: 42 index2013: 37 index2014: 33 index2015: 33 index2016: 31 index2017: 32 index2018: 38 index2019: 36 index2020: 38 index2021: 36 index2022: 36 index2023: 39 index2024: 37 index2025: 37 index102030405019851999201320251985: 25 index1986: 33 index1987: 28 index1988: 40 index1989: 43 index1990: 41 index1991: 19 index1992: 30 index1993: 29 index1994: 28 index1995: 29 index1996: 31 index1997: 32 index1998: 32 index1999: 39 index2000: 32 index2001: 39 index2002: 39 index2003: 39 index2004: 41 index2005: 45 index2006: 40 index2007: 40 index2008: 41 index2009: 36 index2010: 40 index2011: 38 index2012: 42 index2013: 37 index2014: 33 index2015: 33 index2016: 31 index2017: 32 index2018: 38 index2019: 36 index2020: 38 index2021: 36 index2022: 36 index2023: 39 index2024: 37 index2025: 37 index
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 41 values
Periodindex
202537
202437
202339
202236
202136
202038
201936
201838
201732
201631
201533
201433
201337
201242
201138
201040
200936
200841
200740
200640
200545
200441
200339
200239
200139
200032
199939
199832
199732
199631
199529
199428
199329
199230
199119
199041
198943
198840
198728
198633
198525

Merrimack County compared with nearby places

Belknap County: 32 indexCheshire County: 37 indexCoos County: 44 indexGrafton County: 36 indexHillsborough County: 38 indexMerrimack County: 37 indexRockingham County: 38 index
  • Under 36
  • 36 to 37
  • 37 to 38
  • 38 and over
  • No data
Median Air Quality Index (US EPA), 2025, index. Merrimack County is outlined. Same source and period for every area shown. Source: U.S. Environmental Protection Agency. Boundaries: U.S. Census Bureau cartographic boundary files.

Rankings

Definition

Median of the daily Air Quality Index (AQI) values of a US county over the days of the year with an AQI, from the EPA AirData annual summaries.

More on how it is measured
  • The daily county AQI is the highest AQI among the monitors and pollutants reported that day (ozone, PM2.5, PM10, carbon monoxide and nitrogen dioxide).
  • Lower is cleaner: 0 to 50 is good, 51 to 100 moderate and above 100 unhealthy for sensitive groups.

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.

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How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median 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: median daily AQI (Median Air Quality Index (US EPA), Merrimack County, 1985 to 2025) [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: median daily AQI, Median Air Quality Index (US EPA), Merrimack County, 1985 to 2025. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/en/median-air-quality-index/merrimack-county-new-hampshire. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Median Air Quality Index (US EPA), Merrimack County, 1985 to 2025. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/en/median-air-quality-index/merrimack-county-new-hampshire.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Merrimack County, 1985 to 2025 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/median-air-quality-index/merrimack-county-new-hampshire (Accessed: 12 October 2026).

BibTeX
@misc{environmental_median_air_quality_index_2025,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Median Air Quality Index (US EPA), Merrimack County, 1985 to 2025}},
  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/en/median-air-quality-index/merrimack-county-new-hampshire. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median 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: median daily AQI: Median Air Quality Index (US EPA), Merrimack County, 1985 to 2025
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/en/median-air-quality-index/merrimack-county-new-hampshire
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/merrimack-county-new-hampshire.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Questions

What is the median Air Quality Index (US EPA) in Merrimack County?

Median Air Quality Index (US EPA) in Merrimack County was 37 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged from 2024.

Where does this figure come from?

U.S. Environmental Protection Agency. EPA AirData annual AQI by county: median daily AQI. Retrieved by Invokely on 2026-10-12.

What was the highest median Air Quality Index (US EPA) in Merrimack County?

45 in 2005, the highest value since 1985 in this series.

Related statistics for Merrimack County

All statistics for Merrimack County | Merrimack County in figures