EnviroNearby

Cheshire County, New Hampshire air quality history

Daily Air Quality Index summaries from EPA monitors in Cheshire, New Hampshire, 1980–2025.

79%
Good days in 2025
37
Median daily AQI, 2025
2
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Cheshire, New Hampshire on 365 days. 288 of those days (79%) were in the Good range, and the median daily AQI was 37. That median is about the same as the typical monitored county in New Hampshire (median 37 across 7 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 216 days. Across the years with fuller monitoring, the share of Good days rose: an average of 73% in 1980–1982 versus 77% in 2023–2025.

Years with fewer than 120 monitored days (1983) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1980: Good 276 of 362 days1980: Moderate 84 of 362 days1980: Unhealthy for Sensitive Groups 2 of 362 days19801981: Good 130 of 176 days1981: Moderate 43 of 176 days1981: Unhealthy for Sensitive Groups 1 of 176 days1981: Unhealthy 2 of 176 days1982: Good 110 of 160 days1982: Moderate 33 of 160 days1982: Unhealthy for Sensitive Groups 11 of 160 days1982: Unhealthy 5 of 160 days1982: Very Unhealthy 1 of 160 days1983: Good 65 of 88 days1983: Moderate 17 of 88 days1983: Unhealthy for Sensitive Groups 5 of 88 days1983: Unhealthy 1 of 88 days1990: Good 199 of 231 days1990: Moderate 24 of 231 days1990: Unhealthy for Sensitive Groups 8 of 231 days1991: Good 202 of 237 days1991: Moderate 26 of 237 days1991: Unhealthy for Sensitive Groups 7 of 237 days1991: Unhealthy 2 of 237 days19911992: Good 215 of 234 days1992: Moderate 11 of 234 days1992: Unhealthy for Sensitive Groups 7 of 234 days1992: Unhealthy 1 of 234 days1993: Good 209 of 239 days1993: Moderate 22 of 239 days1993: Unhealthy for Sensitive Groups 6 of 239 days1993: Unhealthy 2 of 239 days1994: Good 189 of 231 days1994: Moderate 31 of 231 days1994: Unhealthy for Sensitive Groups 11 of 231 days1995: Good 199 of 228 days1995: Moderate 25 of 228 days1995: Unhealthy for Sensitive Groups 4 of 228 days1996: Good 206 of 225 days1996: Moderate 14 of 225 days1996: Unhealthy for Sensitive Groups 4 of 225 days1996: Unhealthy 1 of 225 days19961997: Good 184 of 201 days1997: Moderate 12 of 201 days1997: Unhealthy for Sensitive Groups 4 of 201 days1997: Unhealthy 1 of 201 days1998: Good 204 of 238 days1998: Moderate 29 of 238 days1998: Unhealthy for Sensitive Groups 5 of 238 days1999: Good 163 of 216 days1999: Moderate 43 of 216 days1999: Unhealthy for Sensitive Groups 9 of 216 days1999: Unhealthy 1 of 216 days2000: Good 207 of 242 days2000: Moderate 34 of 242 days2000: Unhealthy 1 of 242 days2001: Good 150 of 210 days2001: Moderate 55 of 210 days2001: Unhealthy for Sensitive Groups 4 of 210 days2001: Unhealthy 1 of 210 days20012002: Good 153 of 211 days2002: Moderate 47 of 211 days2002: Unhealthy for Sensitive Groups 9 of 211 days2002: Unhealthy 2 of 211 days2003: Good 159 of 213 days2003: Moderate 50 of 213 days2003: Unhealthy for Sensitive Groups 4 of 213 days2004: Good 173 of 205 days2004: Moderate 29 of 205 days2004: Unhealthy for Sensitive Groups 3 of 205 days2005: Good 160 of 212 days2005: Moderate 48 of 212 days2005: Unhealthy for Sensitive Groups 4 of 212 days2006: Good 166 of 214 days2006: Moderate 46 of 214 days2006: Unhealthy for Sensitive Groups 2 of 214 days20062007: Good 157 of 212 days2007: Moderate 50 of 212 days2007: Unhealthy for Sensitive Groups 5 of 212 days2008: Good 201 of 290 days2008: Moderate 86 of 290 days2008: Unhealthy for Sensitive Groups 3 of 290 days2009: Good 212 of 360 days2009: Moderate 146 of 360 days2009: Unhealthy for Sensitive Groups 2 of 360 days2010: Good 236 of 365 days2010: Moderate 128 of 365 days2010: Unhealthy for Sensitive Groups 1 of 365 days2011: Good 209 of 365 days2011: Moderate 152 of 365 days2011: Unhealthy for Sensitive Groups 4 of 365 days20112012: Good 259 of 366 days2012: Moderate 105 of 366 days2012: Unhealthy for Sensitive Groups 2 of 366 days2013: Good 241 of 365 days2013: Moderate 121 of 365 days2013: Unhealthy for Sensitive Groups 3 of 365 days2014: Good 207 of 365 days2014: Moderate 157 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 224 of 365 days2015: Moderate 140 of 365 days2015: Unhealthy 1 of 365 days2016: Good 290 of 366 days2016: Moderate 75 of 366 days2016: Unhealthy for Sensitive Groups 1 of 366 days20162017: Good 298 of 364 days2017: Moderate 66 of 364 days2018: Good 300 of 365 days2018: Moderate 65 of 365 days2019: Good 331 of 365 days2019: Moderate 34 of 365 days2020: Good 299 of 366 days2020: Moderate 67 of 366 days2021: Good 263 of 364 days2021: Moderate 100 of 364 days2021: Unhealthy for Sensitive Groups 1 of 364 days20212022: Good 304 of 365 days2022: Moderate 61 of 365 days2023: Good 253 of 363 days2023: Moderate 108 of 363 days2023: Unhealthy for Sensitive Groups 2 of 363 days2024: Good 302 of 366 days2024: Moderate 64 of 366 days2025: Good 288 of 365 days2025: Moderate 75 of 365 days2025: Unhealthy for Sensitive Groups 2 of 365 days2025
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001501980: 90th percentile AQI 661981: 90th percentile AQI 731982: 90th percentile AQI 1081983: 90th percentile AQI 931990: 90th percentile AQI 641991: 90th percentile AQI 741992: 90th percentile AQI 481993: 90th percentile AQI 611994: 90th percentile AQI 711995: 90th percentile AQI 581996: 90th percentile AQI 501997: 90th percentile AQI 491998: 90th percentile AQI 541999: 90th percentile AQI 742000: 90th percentile AQI 612001: 90th percentile AQI 712002: 90th percentile AQI 672003: 90th percentile AQI 732004: 90th percentile AQI 612005: 90th percentile AQI 742006: 90th percentile AQI 672007: 90th percentile AQI 712008: 90th percentile AQI 712009: 90th percentile AQI 742010: 90th percentile AQI 692011: 90th percentile AQI 762012: 90th percentile AQI 682013: 90th percentile AQI 682014: 90th percentile AQI 672015: 90th percentile AQI 652016: 90th percentile AQI 582017: 90th percentile AQI 572018: 90th percentile AQI 552019: 90th percentile AQI 502020: 90th percentile AQI 552021: 90th percentile AQI 592022: 90th percentile AQI 552023: 90th percentile AQI 612024: 90th percentile AQI 542025: 90th percentile AQI 571980: Median AQI 331981: Median AQI 391982: Median AQI 441983: Median AQI 401990: Median AQI 341991: Median AQI 371992: Median AQI 321993: Median AQI 331994: Median AQI 371995: Median AQI 351996: Median AQI 361997: Median AQI 341998: Median AQI 361999: Median AQI 392000: Median AQI 342001: Median AQI 412002: Median AQI 402003: Median AQI 412004: Median AQI 362005: Median AQI 412006: Median AQI 392007: Median AQI 392008: Median AQI 422009: Median AQI 452010: Median AQI 422011: Median AQI 452012: Median AQI 402013: Median AQI 432014: Median AQI 452015: Median AQI 442016: Median AQI 372017: Median AQI 372018: Median AQI 362019: Median AQI 352020: Median AQI 372021: Median AQI 402022: Median AQI 372023: Median AQI 412024: Median AQI 362025: Median AQI 37198019911996200120062011201620212025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Ozone21659%
Fine particles (PM2.5)14941%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253652887520003757115Ozone
2024366302640000365493Ozone
202336325310820004161125PM2.5
2022365304610000375584Ozone
202136426310010004059127PM2.5
2020366299670000375578PM2.5
2019365331340000355082Ozone
2018365300650000365586Ozone
2017364298660000375793Ozone
20163662907510003758105Ozone
201536522414001004465155PM2.5
201436520715710004567115PM2.5
201336524112130004368108PM2.5
201236625910520004068112Ozone
201136520915240004576134PM2.5
201036523612810004269106PM2.5
200936021214620004574102PM2.5
20082902018630004271133Ozone
20072121575050003971143Ozone
20062141664620003967115Ozone
20052121604840004174143Ozone
20042051732930003661136Ozone
20032131595040004173136Ozone
20022111534792004067182Ozone
20012101505541004171179Ozone
20002422073401003461166Ozone
19992161634391003974159Ozone
19982382042950003654150Ozone
19972011841241003449185Ozone
19962252061441003650161Ozone
19952281992540003558112Ozone
199423118931110003771143Ozone
19932392092262003361172Ozone
19922342151171003248151Ozone
19912372022672003774177Ozone
19902311992480003464140Ozone
198388651751004093164Ozone
1982160110331151044108208Ozone
19811761304312003973185CO
19803622768420003366140CO

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in New Hampshire with a similar median AQI in 2025

All monitored counties in New Hampshire

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem