EnviroNearby

Coos County, New Hampshire air quality history

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

81%
Good days in 2025
44
Median daily AQI, 2025
4
Days above 100 in 2025
345
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Coos, New Hampshire on 345 days. 281 of those days (81%) were in the Good range, and the median daily AQI was 44. That median is higher than the typical monitored county in New Hampshire (median 37 across 7 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 310 days. Across the years with fuller monitoring, the share of Good days fell: an average of 89% in 1981–1983 versus 83% in 2023–2025.

Years with fewer than 120 monitored days (1980) 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 9 of 29 days1980: Moderate 19 of 29 days1980: Unhealthy for Sensitive Groups 1 of 29 days19801981: Good 150 of 173 days1981: Moderate 19 of 173 days1981: Unhealthy for Sensitive Groups 4 of 173 days1982: Good 113 of 124 days1982: Moderate 7 of 124 days1982: Unhealthy for Sensitive Groups 2 of 124 days1982: Unhealthy 2 of 124 days1983: Good 173 of 194 days1983: Moderate 19 of 194 days1983: Unhealthy for Sensitive Groups 2 of 194 days1984: Good 180 of 218 days1984: Moderate 35 of 218 days1984: Unhealthy for Sensitive Groups 3 of 218 days1985: Good 252 of 299 days1985: Moderate 45 of 299 days1985: Unhealthy for Sensitive Groups 1 of 299 days1985: Unhealthy 1 of 299 days19851986: Good 274 of 350 days1986: Moderate 75 of 350 days1986: Unhealthy for Sensitive Groups 1 of 350 days1987: Good 281 of 338 days1987: Moderate 51 of 338 days1987: Unhealthy for Sensitive Groups 6 of 338 days1988: Good 275 of 332 days1988: Moderate 57 of 332 days1989: Good 274 of 345 days1989: Moderate 70 of 345 days1989: Unhealthy for Sensitive Groups 1 of 345 days1990: Good 290 of 349 days1990: Moderate 59 of 349 days19901991: Good 268 of 344 days1991: Moderate 60 of 344 days1991: Unhealthy for Sensitive Groups 11 of 344 days1991: Unhealthy 5 of 344 days1992: Good 236 of 281 days1992: Moderate 40 of 281 days1992: Unhealthy for Sensitive Groups 4 of 281 days1992: Unhealthy 1 of 281 days1993: Good 133 of 175 days1993: Moderate 36 of 175 days1993: Unhealthy for Sensitive Groups 6 of 175 days1994: Good 124 of 178 days1994: Moderate 47 of 178 days1994: Unhealthy for Sensitive Groups 7 of 178 days1995: Good 107 of 171 days1995: Moderate 52 of 171 days1995: Unhealthy for Sensitive Groups 12 of 171 days19951996: Good 101 of 161 days1996: Moderate 50 of 161 days1996: Unhealthy for Sensitive Groups 10 of 161 days1997: Good 119 of 175 days1997: Moderate 45 of 175 days1997: Unhealthy for Sensitive Groups 9 of 175 days1997: Unhealthy 2 of 175 days1998: Good 106 of 169 days1998: Moderate 57 of 169 days1998: Unhealthy for Sensitive Groups 6 of 169 days1999: Good 91 of 207 days1999: Moderate 97 of 207 days1999: Unhealthy for Sensitive Groups 16 of 207 days1999: Unhealthy 3 of 207 days2000: Good 129 of 202 days2000: Moderate 72 of 202 days2000: Unhealthy for Sensitive Groups 1 of 202 days20002001: Good 104 of 206 days2001: Moderate 87 of 206 days2001: Unhealthy for Sensitive Groups 15 of 206 days2002: Good 131 of 220 days2002: Moderate 70 of 220 days2002: Unhealthy for Sensitive Groups 16 of 220 days2002: Unhealthy 1 of 220 days2002: Very Unhealthy 2 of 220 days2003: Good 143 of 245 days2003: Moderate 88 of 245 days2003: Unhealthy for Sensitive Groups 14 of 245 days2004: Good 131 of 246 days2004: Moderate 104 of 246 days2004: Unhealthy for Sensitive Groups 8 of 246 days2004: Unhealthy 3 of 246 days2005: Good 129 of 244 days2005: Moderate 101 of 244 days2005: Unhealthy for Sensitive Groups 14 of 244 days20052006: Good 165 of 245 days2006: Moderate 77 of 245 days2006: Unhealthy for Sensitive Groups 3 of 245 days2007: Good 157 of 242 days2007: Moderate 70 of 242 days2007: Unhealthy for Sensitive Groups 12 of 242 days2007: Unhealthy 3 of 242 days2008: Good 161 of 234 days2008: Moderate 64 of 234 days2008: Unhealthy for Sensitive Groups 9 of 234 days2009: Good 257 of 304 days2009: Moderate 46 of 304 days2009: Unhealthy for Sensitive Groups 1 of 304 days2010: Good 294 of 362 days2010: Moderate 63 of 362 days2010: Unhealthy for Sensitive Groups 5 of 362 days20102011: Good 266 of 356 days2011: Moderate 88 of 356 days2011: Unhealthy for Sensitive Groups 2 of 356 days2012: Good 267 of 365 days2012: Moderate 94 of 365 days2012: Unhealthy for Sensitive Groups 4 of 365 days2013: Good 278 of 365 days2013: Moderate 85 of 365 days2013: Unhealthy for Sensitive Groups 2 of 365 days2014: Good 311 of 365 days2014: Moderate 54 of 365 days2015: Good 285 of 354 days2015: Moderate 62 of 354 days2015: Unhealthy for Sensitive Groups 7 of 354 days20152016: Good 303 of 365 days2016: Moderate 58 of 365 days2016: Unhealthy for Sensitive Groups 4 of 365 days2017: Good 290 of 356 days2017: Moderate 63 of 356 days2017: Unhealthy for Sensitive Groups 2 of 356 days2017: Unhealthy 1 of 356 days2018: Good 222 of 271 days2018: Moderate 46 of 271 days2018: Unhealthy for Sensitive Groups 3 of 271 days2019: Good 313 of 324 days2019: Moderate 11 of 324 days2020: Good 339 of 366 days2020: Moderate 27 of 366 days20202021: Good 325 of 360 days2021: Moderate 33 of 360 days2021: Unhealthy for Sensitive Groups 2 of 360 days2022: Good 350 of 359 days2022: Moderate 9 of 359 days2023: Good 318 of 364 days2023: Moderate 42 of 364 days2023: Unhealthy for Sensitive Groups 4 of 364 days2024: Good 296 of 365 days2024: Moderate 69 of 365 days2025: Good 281 of 345 days2025: Moderate 60 of 345 days2025: Unhealthy for Sensitive Groups 4 of 345 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 year0501001980: 90th percentile AQI 961981: 90th percentile AQI 541982: 90th percentile AQI 501983: 90th percentile AQI 511984: 90th percentile AQI 611985: 90th percentile AQI 541986: 90th percentile AQI 571987: 90th percentile AQI 541988: 90th percentile AQI 551989: 90th percentile AQI 561990: 90th percentile AQI 541991: 90th percentile AQI 671992: 90th percentile AQI 541993: 90th percentile AQI 771994: 90th percentile AQI 801995: 90th percentile AQI 871996: 90th percentile AQI 841997: 90th percentile AQI 841998: 90th percentile AQI 871999: 90th percentile AQI 972000: 90th percentile AQI 682001: 90th percentile AQI 972002: 90th percentile AQI 972003: 90th percentile AQI 822004: 90th percentile AQI 802005: 90th percentile AQI 832006: 90th percentile AQI 672007: 90th percentile AQI 902008: 90th percentile AQI 802009: 90th percentile AQI 582010: 90th percentile AQI 642011: 90th percentile AQI 672012: 90th percentile AQI 672013: 90th percentile AQI 642014: 90th percentile AQI 542015: 90th percentile AQI 582016: 90th percentile AQI 612017: 90th percentile AQI 612018: 90th percentile AQI 642019: 90th percentile AQI 472020: 90th percentile AQI 502021: 90th percentile AQI 502022: 90th percentile AQI 462023: 90th percentile AQI 542024: 90th percentile AQI 582025: 90th percentile AQI 611980: Median AQI 621981: Median AQI 341982: Median AQI 351983: Median AQI 301984: Median AQI 341985: Median AQI 361986: Median AQI 361987: Median AQI 371988: Median AQI 331989: Median AQI 341990: Median AQI 341991: Median AQI 361992: Median AQI 361993: Median AQI 411994: Median AQI 431995: Median AQI 461996: Median AQI 441997: Median AQI 431998: Median AQI 431999: Median AQI 532000: Median AQI 442001: Median AQI 502002: Median AQI 452003: Median AQI 482004: Median AQI 492005: Median AQI 502006: Median AQI 442007: Median AQI 432008: Median AQI 422009: Median AQI 402010: Median AQI 442011: Median AQI 442012: Median AQI 452013: Median AQI 442014: Median AQI 432015: Median AQI 452016: Median AQI 442017: Median AQI 432018: Median AQI 442019: Median AQI 402020: Median AQI 432021: Median AQI 422022: Median AQI 402023: Median AQI 432024: Median AQI 442025: Median AQI 441980198519901995200020052010201520202025
  • 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
Ozone31090%
Carbon monoxide (CO)247%
Fine particles (PM2.5)113%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253452816040004461119Ozone
2024365296690000445890Ozone
20233643184240004354136Ozone
202235935090000404664Ozone
20213603253320004250133Ozone
2020366339270000435074Ozone
2019324313110000404764Ozone
20182712224630004464115Ozone
20173562906321004361174Ozone
20163653035840004461119Ozone
20153542856270004558140Ozone
2014365311540000435497Ozone
20133652788520004464119Ozone
20123652679440004567108Ozone
20113562668820004467101Ozone
20103622946350004464129Ozone
20093042574610004058108Ozone
20082341616490004280150Ozone
200724215770123004390164Ozone
20062451657730004467129Ozone
2005244129101140005083140Ozone
200424613110483004980159Ozone
200324514388140004882129Ozone
200222013170161204597204Ozone
200120610487150005097150Ozone
20002021297210004468112Ozone
19992079197163005397164Ozone
19981691065760004387136Ozone
19971751194592004384187Ozone
199616110150100004484129Ozone
199517110752120004687143Ozone
19941781244770004380119Ozone
19931751333660004177136Ozone
19922812364041003654159PM10
199134426860115003667164PM10
1990349290590000345480PM10
19893452747010003456132PM10
1988332275570000335574PM10
19873382815160003754126PM10
19863502747510003657115PM10
19852992524511003654151PM10
19842181803530003461143Ozone
19831941731920003051126Ozone
1982124113722003550156Ozone
19811731501940003454147Ozone
19802991910006296106CO

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