Median AQI
36
Good
Maine · County air quality · 2025
Aroostook County, Maine
Median AQI 36 (Good). 84.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 36
- Median AQI
- 84.1%
- Good-air days
- 0
- Unhealthy days
- 63%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Aroostook County's air is good on balance, cleaner than the median US county, a median AQI of 36 with 84.1% of 182 monitored days in the Good band, driven mainly by Ozone.
- 36
- median AQI · Good
- 84.1%
- days rated Good
- Ozone
- main pollutant
- 63%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 131.
Data updated July 2026
- Good · 153 d · 84.1%
- Moderate · 27 d · 14.8%
- USG · 2 d · 1.1%
How did Aroostook County's air break down in 2025?
Across 182 monitored days, 153 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 131 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 182 days monitored. Median AQI: 36 (Good).
Insights: Aroostook County, Maine. EPA monitors recorded a median Air Quality Index of 36 across 182 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 153 (84%) fell in the Good band (AQI 0–50), 27 (15%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 53, while the worst single-day peak hit 131 (USG). Residents averaged about 25.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (100 days), PM2.5 (72 days), PM10 (9 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by -163 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 131, usg but never Unhealthy. Nearby counties show comparable readings: Androscoggin (85.5% good, AQI 35); Cumberland (74.0% good, AQI 39); Hancock (89.1% good, AQI 37); Kennebec (83.5% good, AQI 36); Knox (97.3% good, AQI 34); Oxford (74.0% good, AQI 39).
Air Quality Summary
Good Days
84.1%
153 of 182 monitored days
9.1pp vs 75% target
Max AQI Recorded
131
USG
Health Grade
Good
90th-pct AQI 53
Aroostook County, Good days share 84.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Aroostook 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 182 monitored days across EPA AQI categories.
Good
153
84%
Moderate
27
15%
USG
2
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Aroostook County.
- Ozone · 100 days · 54.9%
- PM2.5 · 72 days · 39.6%
- PM10 · 9 days · 4.9%
- CO · 1 days · 0.5%
Health Impact Assessment
Good
Aroostook County's air quality is rated Good based on 84.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 84.1% of monitored days in 2025, with a median AQI of 36. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 100 of 182 monitored days.
5-Year Air Quality Trend
Air quality is stable in Aroostook County. Best year: 2020 (316 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 316 | 49 | 0 | 0 | 36 | 205 |
| 2021 | 305 | 58 | 1 | 1 | 35 | 182 |
| 2022 | 304 | 60 | 0 | 0 | 34 | 80 |
| 2023 | 277 | 85 | 3 | 0 | 37 | 142 |
| 2024 | 299 | 67 | 0 | 0 | 35 | 96 |
| 2025 | 153 | 27 | 2 | 0 | 36 | 131 |
How does Aroostook County compare?
How Aroostook County compares
Good-day share better than US avg
Aroostook County 84.1%
Androscoggin County, Maine 85.5%
US average 76.5%
Median AQI better than US avg
Aroostook County 36
Androscoggin County, Maine 35
US average 38
Unhealthy days / yr about average
Aroostook County 0
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 Aroostook County.
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
Fauquier County, Virginia
AQI 36 · 97.2% good
What Aroostook 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 36 means for exposure. Health guidance
- See how Aroostook County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Aroostook County with its Maine neighbours before drawing a conclusion about the region. All of Maine
Based on 182 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 Aroostook County, Maine? ▼
Aroostook County has a median Air Quality Index (AQI) of 36, rated "Good." 84.1% of monitored days (153 out of 182) had good air quality in 2025.
What is the main pollutant in Aroostook County? ▼
The primary pollutant in Aroostook County is Ozone (O3), which was the main AQI driver on 100 days (55% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Aroostook County have? ▼
In 2025, Aroostook County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 131.
Is the air quality in Aroostook County getting better or worse? ▼
Air quality in Aroostook County is stable based on 5-year trends (2020-2025). Best year: 2020 with 316 good days. Worst year: 2025 with 153 good days.
What does AQI 36 mean for health? ▼
Aroostook 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 Aroostook County compare to other counties in Maine? ▼
Aroostook County has 84.1% good air days. Nearby counties in Maine: Androscoggin (85.5% good), Cumberland (74.0% good), Hancock (89.1% good), Kennebec (83.5% good), Knox (97.3% good), Oxford (74.0% good).
What is the 90th percentile AQI in Aroostook County? ▼
The 90th percentile AQI for Aroostook County is 53, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 131 (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.
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.