EnviroNearby

York County, Maine air quality history

Daily Air Quality Index summaries from EPA monitors in York, Maine, 1982–2025.

97%
Good days in 2025
34
Median daily AQI, 2025
3
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 York, Maine on 365 days. 353 of those days (97%) were in the Good range, and the median daily AQI was 34. That median is about the same as the typical monitored county in Maine (median 34 across 11 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 365 days. Across the years with fuller monitoring, the share of Good days rose: an average of 67% in 1983–1985 versus 95% in 2023–2025.

Years with fewer than 120 monitored days (1982) 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%1982: Good 97 of 115 days1982: Moderate 6 of 115 days1982: Unhealthy for Sensitive Groups 8 of 115 days1982: Unhealthy 3 of 115 days1982: Very Unhealthy 1 of 115 days19821983: Good 121 of 162 days1983: Moderate 16 of 162 days1983: Unhealthy for Sensitive Groups 11 of 162 days1983: Unhealthy 9 of 162 days1983: Very Unhealthy 5 of 162 days1984: Good 107 of 168 days1984: Moderate 30 of 168 days1984: Unhealthy for Sensitive Groups 15 of 168 days1984: Unhealthy 11 of 168 days1984: Very Unhealthy 5 of 168 days1985: Good 103 of 166 days1985: Moderate 24 of 166 days1985: Unhealthy for Sensitive Groups 24 of 166 days1985: Unhealthy 9 of 166 days1985: Very Unhealthy 6 of 166 days1986: Good 142 of 180 days1986: Moderate 23 of 180 days1986: Unhealthy for Sensitive Groups 11 of 180 days1986: Unhealthy 3 of 180 days1986: Very Unhealthy 1 of 180 days1987: Good 139 of 181 days1987: Moderate 26 of 181 days1987: Unhealthy for Sensitive Groups 9 of 181 days1987: Unhealthy 3 of 181 days1987: Very Unhealthy 4 of 181 days19871988: Good 114 of 175 days1988: Moderate 22 of 175 days1988: Unhealthy for Sensitive Groups 11 of 175 days1988: Unhealthy 17 of 175 days1988: Very Unhealthy 11 of 175 days1989: Good 126 of 177 days1989: Moderate 34 of 177 days1989: Unhealthy for Sensitive Groups 8 of 177 days1989: Unhealthy 5 of 177 days1989: Very Unhealthy 4 of 177 days1990: Good 144 of 198 days1990: Moderate 33 of 198 days1990: Unhealthy for Sensitive Groups 10 of 198 days1990: Unhealthy 7 of 198 days1990: Very Unhealthy 4 of 198 days1991: Good 154 of 211 days1991: Moderate 33 of 211 days1991: Unhealthy for Sensitive Groups 15 of 211 days1991: Unhealthy 5 of 211 days1991: Very Unhealthy 4 of 211 days1992: Good 162 of 208 days1992: Moderate 25 of 208 days1992: Unhealthy for Sensitive Groups 11 of 208 days1992: Unhealthy 8 of 208 days1992: Very Unhealthy 2 of 208 days19921993: Good 149 of 197 days1993: Moderate 28 of 197 days1993: Unhealthy for Sensitive Groups 10 of 197 days1993: Unhealthy 10 of 197 days1994: Good 144 of 199 days1994: Moderate 36 of 199 days1994: Unhealthy for Sensitive Groups 13 of 199 days1994: Unhealthy 5 of 199 days1994: Very Unhealthy 1 of 199 days1995: Good 225 of 263 days1995: Moderate 17 of 263 days1995: Unhealthy for Sensitive Groups 13 of 263 days1995: Unhealthy 5 of 263 days1995: Very Unhealthy 3 of 263 days1996: Good 304 of 359 days1996: Moderate 42 of 359 days1996: Unhealthy for Sensitive Groups 10 of 359 days1996: Unhealthy 3 of 359 days1997: Good 314 of 360 days1997: Moderate 31 of 360 days1997: Unhealthy for Sensitive Groups 8 of 360 days1997: Unhealthy 4 of 360 days1997: Very Unhealthy 3 of 360 days19971998: Good 294 of 360 days1998: Moderate 49 of 360 days1998: Unhealthy for Sensitive Groups 11 of 360 days1998: Unhealthy 5 of 360 days1998: Very Unhealthy 1 of 360 days1999: Good 266 of 320 days1999: Moderate 31 of 320 days1999: Unhealthy for Sensitive Groups 19 of 320 days1999: Unhealthy 3 of 320 days1999: Very Unhealthy 1 of 320 days2000: Good 322 of 361 days2000: Moderate 35 of 361 days2000: Unhealthy for Sensitive Groups 3 of 361 days2000: Unhealthy 1 of 361 days2001: Good 285 of 326 days2001: Moderate 24 of 326 days2001: Unhealthy for Sensitive Groups 9 of 326 days2001: Unhealthy 7 of 326 days2001: Very Unhealthy 1 of 326 days2002: Good 312 of 365 days2002: Moderate 28 of 365 days2002: Unhealthy for Sensitive Groups 10 of 365 days2002: Unhealthy 11 of 365 days2002: Very Unhealthy 4 of 365 days20022003: Good 314 of 358 days2003: Moderate 33 of 358 days2003: Unhealthy for Sensitive Groups 9 of 358 days2003: Unhealthy 2 of 358 days2004: Good 223 of 268 days2004: Moderate 36 of 268 days2004: Unhealthy for Sensitive Groups 8 of 268 days2004: Unhealthy 1 of 268 days2005: Good 134 of 183 days2005: Moderate 36 of 183 days2005: Unhealthy for Sensitive Groups 13 of 183 days2006: Good 144 of 183 days2006: Moderate 31 of 183 days2006: Unhealthy for Sensitive Groups 8 of 183 days2007: Good 240 of 274 days2007: Moderate 20 of 274 days2007: Unhealthy for Sensitive Groups 11 of 274 days2007: Unhealthy 3 of 274 days20072008: Good 328 of 362 days2008: Moderate 29 of 362 days2008: Unhealthy for Sensitive Groups 5 of 362 days2009: Good 338 of 362 days2009: Moderate 20 of 362 days2009: Unhealthy for Sensitive Groups 3 of 362 days2009: Unhealthy 1 of 362 days2010: Good 306 of 352 days2010: Moderate 40 of 352 days2010: Unhealthy for Sensitive Groups 5 of 352 days2010: Unhealthy 1 of 352 days2011: Good 237 of 271 days2011: Moderate 29 of 271 days2011: Unhealthy for Sensitive Groups 4 of 271 days2011: Unhealthy 1 of 271 days2012: Good 183 of 214 days2012: Moderate 26 of 214 days2012: Unhealthy for Sensitive Groups 5 of 214 days20122013: Good 186 of 214 days2013: Moderate 21 of 214 days2013: Unhealthy for Sensitive Groups 7 of 214 days2014: Good 193 of 214 days2014: Moderate 19 of 214 days2014: Unhealthy for Sensitive Groups 2 of 214 days2015: Good 194 of 214 days2015: Moderate 17 of 214 days2015: Unhealthy for Sensitive Groups 3 of 214 days2016: Good 211 of 236 days2016: Moderate 23 of 236 days2016: Unhealthy for Sensitive Groups 2 of 236 days2017: Good 204 of 224 days2017: Moderate 19 of 224 days2017: Unhealthy 1 of 224 days20172018: Good 207 of 227 days2018: Moderate 18 of 227 days2018: Unhealthy for Sensitive Groups 2 of 227 days2019: Good 216 of 231 days2019: Moderate 14 of 231 days2019: Unhealthy for Sensitive Groups 1 of 231 days2020: Good 223 of 235 days2020: Moderate 12 of 235 days2021: Good 217 of 240 days2021: Moderate 20 of 240 days2021: Unhealthy for Sensitive Groups 3 of 240 days2022: Good 230 of 246 days2022: Moderate 14 of 246 days2022: Unhealthy for Sensitive Groups 2 of 246 days20222023: Good 304 of 328 days2023: Moderate 24 of 328 days2024: Good 346 of 361 days2024: Moderate 14 of 361 days2024: Unhealthy for Sensitive Groups 1 of 361 days2025: Good 353 of 365 days2025: Moderate 9 of 365 days2025: Unhealthy for Sensitive Groups 2 of 365 days2025: Unhealthy 1 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 year0501001502001982: 90th percentile AQI 1011983: 90th percentile AQI 1401984: 90th percentile AQI 1501985: 90th percentile AQI 1471986: 90th percentile AQI 901987: 90th percentile AQI 871988: 90th percentile AQI 1851989: 90th percentile AQI 971990: 90th percentile AQI 1081991: 90th percentile AQI 1051992: 90th percentile AQI 1011993: 90th percentile AQI 1051994: 90th percentile AQI 1001995: 90th percentile AQI 771996: 90th percentile AQI 671997: 90th percentile AQI 581998: 90th percentile AQI 671999: 90th percentile AQI 772000: 90th percentile AQI 512001: 90th percentile AQI 672002: 90th percentile AQI 642003: 90th percentile AQI 582004: 90th percentile AQI 642005: 90th percentile AQI 902006: 90th percentile AQI 772007: 90th percentile AQI 542008: 90th percentile AQI 502009: 90th percentile AQI 472010: 90th percentile AQI 542011: 90th percentile AQI 542012: 90th percentile AQI 672013: 90th percentile AQI 542014: 90th percentile AQI 502015: 90th percentile AQI 502016: 90th percentile AQI 542017: 90th percentile AQI 502018: 90th percentile AQI 492019: 90th percentile AQI 482020: 90th percentile AQI 472021: 90th percentile AQI 502022: 90th percentile AQI 492023: 90th percentile AQI 492024: 90th percentile AQI 452025: 90th percentile AQI 451982: Median AQI 311983: Median AQI 371984: Median AQI 411985: Median AQI 461986: Median AQI 411987: Median AQI 391988: Median AQI 441989: Median AQI 431990: Median AQI 401991: Median AQI 401992: Median AQI 391993: Median AQI 371994: Median AQI 401995: Median AQI 341996: Median AQI 341997: Median AQI 341998: Median AQI 331999: Median AQI 342000: Median AQI 322001: Median AQI 322002: Median AQI 332003: Median AQI 332004: Median AQI 362005: Median AQI 422006: Median AQI 402007: Median AQI 332008: Median AQI 352009: Median AQI 332010: Median AQI 362011: Median AQI 362012: Median AQI 412013: Median AQI 402014: Median AQI 392015: Median AQI 402016: Median AQI 382017: Median AQI 372018: Median AQI 402019: Median AQI 382020: Median AQI 392021: Median AQI 372022: Median AQI 382023: Median AQI 352024: Median AQI 342025: Median AQI 341982198719921997200220072012201720222025
  • 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
Ozone365100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365353921003445169Ozone
20243613461410003445129Ozone
2023328304240000354984Ozone
20222462301420003849126Ozone
20212402172030003750129Ozone
2020235223120000394787Ozone
20192312161410003848115Ozone
20182272071820004049119Ozone
20172242041901003750159Ozone
20162362112320003854108Ozone
20152141941730004050136Ozone
20142141931920003950101Ozone
20132141862170004054147Ozone
20122141832650004167140Ozone
20112712372941003654151Ozone
20103523064051003654174Ozone
20093623382031003347154Ozone
20083623282950003550133Ozone
200727424020113003354185Ozone
20061831443180004077140Ozone
200518313436130004290147Ozone
20042682233681003664187Ozone
20033583143392003358169Ozone
2002365312281011403364217Ozone
20013262852497103267202Ozone
20003613223531003251159Ozone
199932026631193103477209Ozone
199836029449115103367207Ozone
19973603143184303458215Ozone
199635930442103003467177Ozone
199526322517135303477217Ozone
1994199144361351040100209Ozone
19931971492810100037105197Ozone
1992208162251182039101206Ozone
1991211154331554040105233Ozone
1990198144331074040108232Ozone
19891771263485404397221Ozone
198817511422111711044185227Ozone
19871811392693403987220Ozone
198618014223113104190212Ozone
1985166103242496046147243Ozone
19841681073015115041150219Ozone
1983162121161195037140222Ozone
1982115976831031101218Ozone

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 Maine with a similar median AQI in 2025

All monitored counties in Maine

Source: U.S. EPA AirData, “Annual AQI by County” files for 1982–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem