Median AQI
38
Good
New York · County air quality · 2025
Westchester County, New York
Median AQI 38 (Good). 82.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 38
- Median AQI
- 82.5%
- Good-air days
- 0
- Unhealthy days
- 62%
- Cleaner than US counties
Westchester County's 2025 annual median AQI is 38 (Good), with 82.5% Good days
According to the U.S. EPA Air Quality System, Westchester County, New York posted a 2025 median AQI of 38 (Good) across 365 monitored days, with 82.5% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Westchester County's 82.5% Good-day share places it cleaner than 62% of US counties in 2025.
- Closest median-AQI peer
- Adams County (94.7% Good, median AQI 38) is the closest nationwide median-AQI peer to Westchester County.
- 2020–2025 trend
- Westchester County's floor-qualifying Good-day share is stable from 2020 to 2025 (84.0% → 82.5%).
- Median AQI
- Median AQI: 38
The verdict
According to EPA Air Quality System monitoring data, Westchester County's air is good on balance, cleaner than the median US county, a median AQI of 38 with 82.5% of 365 monitored days in the Good band, driven mainly by Ozone.
- 38
- median AQI · Good
- 82.5%
- days rated Good
- Ozone
- main pollutant
- 62%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 136.
Data updated August 2026
- Good · 301 d · 82.5%
- Moderate · 58 d · 15.9%
- USG · 6 d · 1.6%
How did Westchester County's air break down in 2025?
Across 365 monitored days, 301 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 136 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 365 days monitored. Median AQI: 38 (Good).
Insights: Westchester County, New York. EPA monitors recorded a median Air Quality Index of 38 across 365 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 301 (82%) fell in the Good band (AQI 0–50), 58 (16%) registered Moderate readings, and 6 (2%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 56, while the worst single-day peak hit 136 (USG). Residents averaged about 24.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (252 days), PM2.5 (113 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -1.6 points and the median AQI moved +0 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 136, usg but never Unhealthy. Nearby counties show comparable readings: Albany (68.5% good, AQI 39); Bronx (59.2% good, AQI 45); Chautauqua (89.0% good, AQI 36); Dutchess (94.0% good, AQI 34); Erie (63.8% good, AQI 44); Essex (83.8% good, AQI 41).
Air Quality Summary
Good Days
82.5%
301 of 365 monitored days
7.5pp vs 75% target
Max AQI Recorded
136
USG
Health Grade
Good
90th-pct AQI 56
Westchester County, Good days share 82.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Westchester County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 365 monitored days across EPA AQI categories.
Good
301
82%
Moderate
58
16%
USG
6
2%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Westchester County.
- Ozone · 252 days · 69.0%
- PM2.5 · 113 days · 31.0%
Health Impact Assessment
Good
Westchester County's air quality is rated Good based on 82.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 82.5% of monitored days in 2025, with a median AQI of 38. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 252 of 365 monitored days.
5-Year Air Quality Trend
Air quality is stable in Westchester County. Highest Good-day share: 2021 (84.1%, 307 of 365 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 305 | 57 | 1 | 0 | 38 | 105 |
| 2021 | 307 | 52 | 6 | 0 | 38 | 143 |
| 2022 | 300 | 65 | 0 | 0 | 38 | 100 |
| 2023 | 287 | 71 | 4 | 3 | 39 | 198 |
| 2024 | 302 | 57 | 6 | 0 | 36 | 143 |
| 2025 | 301 | 58 | 6 | 0 | 38 | 136 |
How does Westchester County compare?
How Westchester County compares
Good-day share better than US avg
Westchester County 82.5%
Adams County, Illinois 94.7%
US average 76.0%
Median AQI better than US avg
Westchester County 38
Adams County, Illinois 38
US average 39
Unhealthy days / yr better than US avg
Westchester County 0
Adams County, Illinois 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Westchester County (38), not geographic neighbors.
Adams County, Illinois
Median AQI 38 · 94.7% Good-day share
Albemarle County, Virginia
Median AQI 38 · 81.0% Good-day share
Alexander County, North Carolina
Median AQI 38 · 93.5% Good-day share
Amador County, California
Median AQI 38 · 87.4% Good-day share
Anoka County, Minnesota
Median AQI 38 · 74.1% Good-day share
Avery County, North Carolina
Median AQI 38 · 92.3% Good-day share
Same primary pollutant: Ozone
Ozone led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Horry County, South Carolina
82.5% Good-day share · median AQI 39
Hancock County, Kentucky
82.6% Good-day share · median AQI 43
Billings County, North Dakota
82.7% Good-day share · median AQI 38
Atlantic County, New Jersey
82.2% Good-day share · median AQI 36
Sussex County, Delaware
82.2% Good-day share · median AQI 39
Calaveras County, California
82.2% Good-day share · median AQI 40
New York counties on the map
Geographic containment only, other monitored counties in New York, independent of AQI or pollutant match.
What Westchester County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 38 means for exposure. Health guidance
- See how Westchester County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Westchester County with its New York neighbours before drawing a conclusion about the region. All of New York
Based on 365 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Westchester County, New York? ▼
Westchester County has a median Air Quality Index (AQI) of 38, rated "Good." 82.5% of monitored days (301 out of 365) had good air quality in 2025.
What is the main pollutant in Westchester County? ▼
The primary pollutant in Westchester County is Ozone (O3), which was the main AQI driver on 252 days (69% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Westchester County have? ▼
In 2025, Westchester County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 136.
Is the air quality in Westchester County getting better or worse? ▼
Air quality in Westchester County is stable across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2021 at 84.1% (307 of 365 days). Lowest qualifying Good-day share: 2023 at 78.6% (287 of 365 days).
What does AQI 38 mean for health? ▼
Westchester County's median AQI of 38 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Westchester County compare to other counties in New York? ▼
Westchester County has 82.5% good air days. Nearby counties in New York: Albany (68.5% good), Bronx (59.2% good), Chautauqua (89.0% good), Dutchess (94.0% good), Erie (63.8% good), Essex (83.8% good).
What is the 90th percentile AQI in Westchester County? ▼
The 90th percentile AQI for Westchester County is 56, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 136 (USG).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Westchester County, New York · 2020–2025
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Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.