EnviroNearby

Windham County, Vermont air quality history

Daily Air Quality Index summaries from EPA monitors in Windham, Vermont, 1982–2025.

97%
Good days in 2024
12
Median daily AQI, 2024
0
Days above 100 in 2024
120
Days with an AQI in 2024 (of 366)

In 2024, EPA reported a daily Air Quality Index (AQI) for Windham, Vermont on 120 days. 116 of those days (97%) were in the Good range, and the median daily AQI was 12. That median is lower than the typical monitored county in Vermont (median 36.5 across 4 counties), and lower than the typical monitored U.S. county (41). The main pollutant was fine particles (PM2.5) on 120 days.

EPA did not report an AQI for every day of 2024 here (120 of 366 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

Years with fewer than 120 monitored days (2019, 2020, 2021, 2022, 2023, 2025…) 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 62 of 75 days1982: Moderate 8 of 75 days1982: Unhealthy for Sensitive Groups 4 of 75 days1982: Unhealthy 1 of 75 days19821983: Good 164 of 190 days1983: Moderate 20 of 190 days1983: Unhealthy for Sensitive Groups 4 of 190 days1983: Unhealthy 2 of 190 days1984: Good 182 of 219 days1984: Moderate 25 of 219 days1984: Unhealthy for Sensitive Groups 9 of 219 days1984: Unhealthy 2 of 219 days1984: Very Unhealthy 1 of 219 days1985: Good 157 of 205 days1985: Moderate 35 of 205 days1985: Unhealthy for Sensitive Groups 8 of 205 days1985: Unhealthy 5 of 205 days1986: Good 46 of 48 days1986: Moderate 2 of 48 days1987: Good 51 of 52 days1987: Moderate 1 of 52 days19871988: Good 55 of 57 days1988: Moderate 2 of 57 days1989: Good 54 of 54 days1990: Good 15 of 15 days1991: Good 50 of 51 days1991: Moderate 1 of 51 days1992: Good 55 of 56 days1992: Moderate 1 of 56 days19921993: Good 58 of 59 days1993: Moderate 1 of 59 days1994: Good 60 of 60 days1995: Good 58 of 58 days1996: Good 60 of 60 days1997: Good 60 of 60 days19972003: Good 5 of 5 days2004: Good 57 of 57 days2005: Good 60 of 60 days2006: Good 60 of 60 days2007: Good 58 of 58 days20072008: Good 51 of 51 days2011: Good 5 of 5 days2012: Good 105 of 113 days2012: Moderate 8 of 113 days2013: Good 113 of 118 days2013: Moderate 5 of 118 days2014: Good 113 of 120 days2014: Moderate 7 of 120 days20142015: Good 105 of 112 days2015: Moderate 7 of 112 days2016: Good 105 of 108 days2016: Moderate 3 of 108 days2017: Good 115 of 118 days2017: Moderate 3 of 118 days2018: Good 112 of 117 days2018: Moderate 5 of 117 days2019: Good 103 of 104 days2019: Moderate 1 of 104 days20192020: Good 113 of 113 days2021: Good 114 of 118 days2021: Moderate 4 of 118 days2022: Good 71 of 71 days2023: Good 112 of 119 days2023: Moderate 7 of 119 days2024: Good 116 of 120 days2024: Moderate 4 of 120 days20242025: Good 92 of 100 days2025: Moderate 7 of 100 days2025: Unhealthy for Sensitive Groups 1 of 100 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 year0501001982: 90th percentile AQI 901983: 90th percentile AQI 581984: 90th percentile AQI 671985: 90th percentile AQI 741986: 90th percentile AQI 401987: 90th percentile AQI 341988: 90th percentile AQI 351989: 90th percentile AQI 341990: 90th percentile AQI 311991: 90th percentile AQI 321992: 90th percentile AQI 351993: 90th percentile AQI 351994: 90th percentile AQI 341995: 90th percentile AQI 321996: 90th percentile AQI 291997: 90th percentile AQI 322003: 90th percentile AQI 382004: 90th percentile AQI 262005: 90th percentile AQI 312006: 90th percentile AQI 242007: 90th percentile AQI 232008: 90th percentile AQI 192011: 90th percentile AQI 142012: 90th percentile AQI 442013: 90th percentile AQI 372014: 90th percentile AQI 462015: 90th percentile AQI 432016: 90th percentile AQI 322017: 90th percentile AQI 342018: 90th percentile AQI 352019: 90th percentile AQI 262020: 90th percentile AQI 252021: 90th percentile AQI 292022: 90th percentile AQI 242023: 90th percentile AQI 382024: 90th percentile AQI 352025: 90th percentile AQI 481982: Median AQI 341983: Median AQI 311984: Median AQI 341985: Median AQI 391986: Median AQI 221987: Median AQI 211988: Median AQI 201989: Median AQI 211990: Median AQI 211991: Median AQI 191992: Median AQI 181993: Median AQI 171994: Median AQI 161995: Median AQI 161996: Median AQI 171997: Median AQI 192003: Median AQI 222004: Median AQI 152005: Median AQI 142006: Median AQI 152007: Median AQI 132008: Median AQI 132011: Median AQI 92012: Median AQI 162013: Median AQI 162014: Median AQI 172015: Median AQI 182016: Median AQI 132017: Median AQI 142018: Median AQI 122019: Median AQI 112020: Median AQI 122021: Median AQI 112022: Median AQI 112023: Median AQI 142024: Median AQI 122025: Median AQI 15198219871992199720072014201920242025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2024

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
Fine particles (PM2.5)120100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202510092710001548117PM2.5
202412011640000123569PM2.5
202311911270000143895PM2.5
2022717100000112444PM2.5
202111811440000112956PM2.5
202011311300000122542PM2.5
201910410310000112652PM2.5
201811711250000123557PM2.5
201711811530000143454PM2.5
201610810530000133258PM2.5
201511210570000184366PM2.5
201412011370000174657PM2.5
201311811350000163758PM2.5
201211310580000164462PM2.5
2011550000091414PM2.5
2008515100000131932PM10
2007585800000132331PM10
2006606000000152434PM10
2005606000000143148PM10
2004575700000152640PM10
20035500000223838PM10
1997606000000193246PM10
1996606000000172940PM10
1995585800000163242PM10
1994606000000163447PM10
1993595810000173552PM10
1992565510000183558PM10
1991515010000193251PM10
1990151500000213148PM10
1989545400000213442PM10
1988575520000203556PM10
1987525110000213454PM10
1986484620000224054PM10
19852051573585003974185Ozone
19842191822592103467207Ozone
19831901642042003158197Ozone
19827562841003490151Ozone

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.

All monitored counties in Vermont

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