Median AQI
36
Good
Maine · County air quality · 2025
York County, Maine
Median AQI 36 (Good). 96.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 36
- Median AQI
- 96.0%
- Good-air days
- 1
- Unhealthy days
- 92%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, York County's air is good on balance, among the cleanest 10% of US counties, a median AQI of 36 with 96.0% of 304 monitored days in the Good band, driven mainly by Ozone.
- 36
- median AQI · Good
- 96.0%
- days rated Good
- Ozone
- main pollutant
- 92%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 169.
Data updated July 2026
- Good · 292 d · 96.1%
- Moderate · 9 d · 3.0%
- USG · 2 d · 0.7%
- Unhealthy · 1 d · 0.3%
How did York County's air break down in 2025?
Across 304 monitored days, 292 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 169 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 304 days monitored. Median AQI: 36 (Good).
Insights: York County, Maine. EPA monitors recorded a median Air Quality Index of 36 across 304 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 292 (96%) fell in the Good band (AQI 0–50), 9 (3%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 46, while the worst single-day peak hit 169 (Unhealthy). Residents averaged about 28.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (304 days). Across the 2020–2025 trend window, good days shifted by +69 and the median AQI moved -3 points, placing the multi-year trajectory at stable. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Androscoggin (85.5% good, AQI 35); Aroostook (84.1% good, AQI 36); Cumberland (74.0% good, AQI 39); Hancock (89.1% good, AQI 37); Kennebec (83.5% good, AQI 36); Knox (97.3% good, AQI 34).
Air Quality Summary
Good Days
96.0%
292 of 304 monitored days
21.0pp vs 75% target
Max AQI Recorded
169
Unhealthy
Health Grade
Excellent
90th-pct AQI 46
York County, Good days share 96.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
York County, Unhealthy-or-worse share 0.3%
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 304 monitored days across EPA AQI categories.
Good
292
96%
Moderate
9
3%
USG
2
1%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in York County.
- Ozone · 304 days · 100.0%
Health Impact Assessment
Excellent
York County's air quality is rated Excellent based on 96.0% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 2 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 169. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 304 of 304 monitored days.
5-Year Air Quality Trend
Air quality is stable in York County. Best year: 2024 (346 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 223 | 12 | 0 | 0 | 39 | 87 |
| 2021 | 217 | 20 | 3 | 0 | 37 | 129 |
| 2022 | 230 | 14 | 2 | 0 | 38 | 126 |
| 2023 | 304 | 24 | 0 | 0 | 35 | 84 |
| 2024 | 346 | 14 | 1 | 0 | 34 | 129 |
| 2025 | 292 | 9 | 2 | 1 | 36 | 169 |
How does York County compare?
How York County compares
Good-day share better than US avg
York County 96.0%
Androscoggin County, Maine 85.5%
US average 76.5%
Median AQI better than US avg
York County 36
Androscoggin County, Maine 35
US average 38
Unhealthy days / yr worse than US avg
York County 1
Androscoggin County, Maine 0
US average 0
Other Counties in Maine
Air quality comparison for nearby counties in Maine.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to York County.
Aroostook County, Maine
AQI 36 · 84.1% good
Berkeley County, South Carolina
AQI 36 · 92.2% good
Carter County, Kentucky
AQI 36 · 89.8% good
Claiborne County, Tennessee
AQI 36 · 96.3% good
Clark County, Illinois
AQI 36 · 92.1% good
Cobb County, Georgia
AQI 36 · 92.5% good
What York County's air means for you
On most days the air here is fine, but Ozone drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 36 means for exposure. Health guidance
- See how York County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare York County with its Maine neighbours before drawing a conclusion about the region. All of Maine
Based on 304 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in York County, Maine? ▼
York County has a median Air Quality Index (AQI) of 36, rated "Good." 96.0% of monitored days (292 out of 304) had good air quality in 2025.
What is the main pollutant in York County? ▼
The primary pollutant in York County is Ozone (O3), which was the main AQI driver on 304 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does York County have? ▼
In 2025, York County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 169.
Is the air quality in York County getting better or worse? ▼
Air quality in York County is stable based on 5-year trends (2020-2025). Best year: 2024 with 346 good days. Worst year: 2021 with 217 good days.
What does AQI 36 mean for health? ▼
York County's median AQI of 36 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does York County compare to other counties in Maine? ▼
York County has 96.0% good air days. Nearby counties in Maine: Androscoggin (85.5% good), Aroostook (84.1% good), Cumberland (74.0% good), Hancock (89.1% good), Kennebec (83.5% good), Knox (97.3% good).
What is the 90th percentile AQI in York County? ▼
The 90th percentile AQI for York County is 46, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 169 (Unhealthy).
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.
Every figure on PlainAir 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.