EnviroNearby

Westchester County, New York air quality history

Daily Air Quality Index summaries from EPA monitors in Westchester, New York, 1980–2025.

82%
Good days in 2025
38
Median daily AQI, 2025
6
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 Westchester, New York on 365 days. 301 of those days (82%) were in the Good range, and the median daily AQI was 38. That median is about the same as the typical monitored county in New York (median 36 across 27 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 252 days. Across the years with fuller monitoring, the share of Good days rose: an average of 77% in 1980–1982 versus 81% in 2023–2025.

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 263 of 365 days1980: Moderate 48 of 365 days1980: Unhealthy for Sensitive Groups 25 of 365 days1980: Unhealthy 15 of 365 days1980: Very Unhealthy 14 of 365 days19801981: Good 302 of 365 days1981: Moderate 47 of 365 days1981: Unhealthy for Sensitive Groups 7 of 365 days1981: Unhealthy 9 of 365 days1982: Good 274 of 365 days1982: Moderate 55 of 365 days1982: Unhealthy for Sensitive Groups 21 of 365 days1982: Unhealthy 8 of 365 days1982: Very Unhealthy 7 of 365 days1983: Good 269 of 365 days1983: Moderate 49 of 365 days1983: Unhealthy for Sensitive Groups 24 of 365 days1983: Unhealthy 13 of 365 days1983: Very Unhealthy 10 of 365 days1984: Good 291 of 356 days1984: Moderate 47 of 356 days1984: Unhealthy for Sensitive Groups 9 of 356 days1984: Unhealthy 8 of 356 days1984: Very Unhealthy 1 of 356 days1985: Good 172 of 224 days1985: Moderate 21 of 224 days1985: Unhealthy for Sensitive Groups 21 of 224 days1985: Unhealthy 9 of 224 days1985: Very Unhealthy 1 of 224 days19851986: Good 312 of 355 days1986: Moderate 27 of 355 days1986: Unhealthy for Sensitive Groups 10 of 355 days1986: Unhealthy 5 of 355 days1986: Very Unhealthy 1 of 355 days1987: Good 305 of 358 days1987: Moderate 26 of 358 days1987: Unhealthy for Sensitive Groups 12 of 358 days1987: Unhealthy 13 of 358 days1987: Very Unhealthy 2 of 358 days1988: Good 296 of 361 days1988: Moderate 22 of 361 days1988: Unhealthy for Sensitive Groups 12 of 361 days1988: Unhealthy 18 of 361 days1988: Very Unhealthy 13 of 361 days1989: Good 297 of 337 days1989: Moderate 22 of 337 days1989: Unhealthy for Sensitive Groups 11 of 337 days1989: Unhealthy 7 of 337 days1990: Good 302 of 355 days1990: Moderate 38 of 355 days1990: Unhealthy for Sensitive Groups 6 of 355 days1990: Unhealthy 9 of 355 days19901991: Good 286 of 360 days1991: Moderate 30 of 360 days1991: Unhealthy for Sensitive Groups 26 of 360 days1991: Unhealthy 13 of 360 days1991: Very Unhealthy 5 of 360 days1992: Good 316 of 363 days1992: Moderate 30 of 363 days1992: Unhealthy for Sensitive Groups 13 of 363 days1992: Unhealthy 3 of 363 days1992: Very Unhealthy 1 of 363 days1993: Good 312 of 362 days1993: Moderate 31 of 362 days1993: Unhealthy for Sensitive Groups 12 of 362 days1993: Unhealthy 7 of 362 days1994: Good 295 of 343 days1994: Moderate 29 of 343 days1994: Unhealthy for Sensitive Groups 13 of 343 days1994: Unhealthy 5 of 343 days1994: Very Unhealthy 1 of 343 days1995: Good 306 of 357 days1995: Moderate 24 of 357 days1995: Unhealthy for Sensitive Groups 18 of 357 days1995: Unhealthy 7 of 357 days1995: Very Unhealthy 2 of 357 days19951996: Good 316 of 358 days1996: Moderate 25 of 358 days1996: Unhealthy for Sensitive Groups 12 of 358 days1996: Unhealthy 5 of 358 days1997: Good 318 of 365 days1997: Moderate 29 of 365 days1997: Unhealthy for Sensitive Groups 7 of 365 days1997: Unhealthy 11 of 365 days1998: Good 280 of 338 days1998: Moderate 41 of 338 days1998: Unhealthy for Sensitive Groups 11 of 338 days1998: Unhealthy 6 of 338 days1999: Good 313 of 358 days1999: Moderate 26 of 358 days1999: Unhealthy for Sensitive Groups 7 of 358 days1999: Unhealthy 7 of 358 days1999: Very Unhealthy 5 of 358 days2000: Good 270 of 355 days2000: Moderate 73 of 355 days2000: Unhealthy for Sensitive Groups 10 of 355 days2000: Unhealthy 1 of 355 days2000: Very Unhealthy 1 of 355 days20002001: Good 240 of 360 days2001: Moderate 97 of 360 days2001: Unhealthy for Sensitive Groups 15 of 360 days2001: Unhealthy 7 of 360 days2001: Very Unhealthy 1 of 360 days2002: Good 244 of 350 days2002: Moderate 71 of 350 days2002: Unhealthy for Sensitive Groups 19 of 350 days2002: Unhealthy 14 of 350 days2002: Very Unhealthy 2 of 350 days2003: Good 277 of 360 days2003: Moderate 67 of 360 days2003: Unhealthy for Sensitive Groups 12 of 360 days2003: Unhealthy 4 of 360 days2004: Good 281 of 350 days2004: Moderate 61 of 350 days2004: Unhealthy for Sensitive Groups 8 of 350 days2005: Good 253 of 364 days2005: Moderate 88 of 364 days2005: Unhealthy for Sensitive Groups 14 of 364 days2005: Unhealthy 8 of 364 days2005: Very Unhealthy 1 of 364 days20052006: Good 261 of 347 days2006: Moderate 72 of 347 days2006: Unhealthy for Sensitive Groups 12 of 347 days2006: Unhealthy 1 of 347 days2006: Very Unhealthy 1 of 347 days2007: Good 200 of 364 days2007: Moderate 145 of 364 days2007: Unhealthy for Sensitive Groups 12 of 364 days2007: Unhealthy 7 of 364 days2008: Good 207 of 365 days2008: Moderate 143 of 365 days2008: Unhealthy for Sensitive Groups 13 of 365 days2008: Unhealthy 2 of 365 days2009: Good 246 of 365 days2009: Moderate 109 of 365 days2009: Unhealthy for Sensitive Groups 10 of 365 days2010: Good 238 of 365 days2010: Moderate 113 of 365 days2010: Unhealthy for Sensitive Groups 14 of 365 days20102011: Good 207 of 362 days2011: Moderate 150 of 362 days2011: Unhealthy for Sensitive Groups 3 of 362 days2011: Unhealthy 2 of 362 days2012: Good 244 of 366 days2012: Moderate 111 of 366 days2012: Unhealthy for Sensitive Groups 10 of 366 days2012: Unhealthy 1 of 366 days2013: Good 249 of 365 days2013: Moderate 110 of 365 days2013: Unhealthy for Sensitive Groups 6 of 365 days2014: Good 237 of 365 days2014: Moderate 124 of 365 days2014: Unhealthy for Sensitive Groups 3 of 365 days2014: Unhealthy 1 of 365 days2015: Good 231 of 365 days2015: Moderate 125 of 365 days2015: Unhealthy for Sensitive Groups 9 of 365 days20152016: Good 269 of 366 days2016: Moderate 91 of 366 days2016: Unhealthy for Sensitive Groups 6 of 366 days2017: Good 292 of 363 days2017: Moderate 66 of 363 days2017: Unhealthy for Sensitive Groups 5 of 363 days2018: Good 295 of 365 days2018: Moderate 58 of 365 days2018: Unhealthy for Sensitive Groups 11 of 365 days2018: Unhealthy 1 of 365 days2019: Good 309 of 365 days2019: Moderate 55 of 365 days2019: Unhealthy for Sensitive Groups 1 of 365 days2020: Good 305 of 363 days2020: Moderate 57 of 363 days2020: Unhealthy for Sensitive Groups 1 of 363 days20202021: Good 307 of 365 days2021: Moderate 52 of 365 days2021: Unhealthy for Sensitive Groups 6 of 365 days2022: Good 300 of 365 days2022: Moderate 65 of 365 days2023: Good 287 of 365 days2023: Moderate 71 of 365 days2023: Unhealthy for Sensitive Groups 4 of 365 days2023: Unhealthy 3 of 365 days2024: Good 302 of 365 days2024: Moderate 57 of 365 days2024: Unhealthy for Sensitive Groups 6 of 365 days2025: Good 301 of 365 days2025: Moderate 58 of 365 days2025: Unhealthy for Sensitive Groups 6 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 1431981: 90th percentile AQI 671982: 90th percentile AQI 1001983: 90th percentile AQI 1261984: 90th percentile AQI 801985: 90th percentile AQI 1151986: 90th percentile AQI 611987: 90th percentile AQI 781988: 90th percentile AQI 1151989: 90th percentile AQI 581990: 90th percentile AQI 671991: 90th percentile AQI 1081992: 90th percentile AQI 581993: 90th percentile AQI 711994: 90th percentile AQI 671995: 90th percentile AQI 841996: 90th percentile AQI 641997: 90th percentile AQI 611998: 90th percentile AQI 771999: 90th percentile AQI 612000: 90th percentile AQI 682001: 90th percentile AQI 872002: 90th percentile AQI 1012003: 90th percentile AQI 712004: 90th percentile AQI 672005: 90th percentile AQI 812006: 90th percentile AQI 742007: 90th percentile AQI 802008: 90th percentile AQI 732009: 90th percentile AQI 712010: 90th percentile AQI 702011: 90th percentile AQI 672012: 90th percentile AQI 702013: 90th percentile AQI 642014: 90th percentile AQI 612015: 90th percentile AQI 642016: 90th percentile AQI 642017: 90th percentile AQI 542018: 90th percentile AQI 612019: 90th percentile AQI 552020: 90th percentile AQI 552021: 90th percentile AQI 562022: 90th percentile AQI 552023: 90th percentile AQI 582024: 90th percentile AQI 582025: 90th percentile AQI 561980: Median AQI 361981: Median AQI 311982: Median AQI 371983: Median AQI 341984: Median AQI 311985: Median AQI 361986: Median AQI 291987: Median AQI 311988: Median AQI 311989: Median AQI 281990: Median AQI 311991: Median AQI 311992: Median AQI 311993: Median AQI 311994: Median AQI 301995: Median AQI 311996: Median AQI 311997: Median AQI 321998: Median AQI 311999: Median AQI 312000: Median AQI 322001: Median AQI 392002: Median AQI 382003: Median AQI 362004: Median AQI 302005: Median AQI 402006: Median AQI 382007: Median AQI 472008: Median AQI 482009: Median AQI 422010: Median AQI 432011: Median AQI 462012: Median AQI 432013: Median AQI 422014: Median AQI 442015: Median AQI 432016: Median AQI 402017: Median AQI 382018: Median AQI 382019: Median AQI 382020: Median AQI 382021: Median AQI 382022: Median AQI 382023: Median AQI 392024: Median AQI 362025: Median AQI 381980198519901995200020052010201520202025
  • 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
Ozone25269%
Fine particles (PM2.5)11331%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253653015860003856136Ozone
20243653025760003658143Ozone
20233652877143003958198Ozone
20223653006500003855100Ozone
20213653075260003856143Ozone
20203633055710003855105Ozone
20193653095510003855105Ozone
201836529558111003861169Ozone
20173632926650003854112Ozone
20163662699160004064140Ozone
201536523112590004364140Ozone
201436523712431004461154PM2.5
201336524911060004264136Ozone
2012366244111101004370151Ozone
201136220715032004667182PM2.5
2010365238113140004370150PM2.5
2009365246109100004271119PM2.5
2008365207143132004873190PM2.5
2007364200145127004780190PM2.5
200634726172121103874207Ozone
200536425388148104081201Ozone
20043502816180003067129Ozone
200336027767124003671179Ozone
20023502447119142038101216Ozone
200136024097157103987202Ozone
200035527073101103268205Ozone
19993583132677503161215Ozone
199833828041116003177172Ozone
199736531829711003261187Ozone
199635831625125003164185Ozone
199535730624187203184204Ozone
199434329529135103067202Ozone
199336231231127003171182Ozone
199236331630133103158217Ozone
19913602863026135031108222Ozone
19903553023869003167195Ozone
198933729722117002858179Ozone
198836129622121813031115239Ozone
1987358305261213203178212Ozone
198635531227105102961209Ozone
1985224172212191036115201Ozone
19843562914798103180207Ozone
198336526949241310034126246Ozone
1982365274552187037100221Ozone
19813653024779003167197Ozone
198036526348251514036143235Ozone

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 York with a similar median AQI in 2025

All monitored counties in New York

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