Median AQI
35
Good
Pennsylvania · County air quality · 2025
Warren County, Pennsylvania
Median AQI 35 (Good). 78.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 35
- Median AQI
- 78.7%
- Good-air days
- 0
- Unhealthy days
- 52%
- Cleaner than US counties
Warren County's 2025 annual median AQI is 35 (Good), with 78.7% Good days
According to the U.S. EPA Air Quality System, Warren County, Pennsylvania posted a 2025 median AQI of 35 (Good) across 150 monitored days, with 78.7% 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
- Warren County's 78.7% Good-day share places it cleaner than 52% of US counties in 2025.
- Closest median-AQI peer
- Atascosa County (76.0% Good, median AQI 35) is the closest nationwide median-AQI peer to Warren County.
- Median AQI
- Median AQI: 35
- Good days
- Good days: 78.7%
The verdict
According to EPA Air Quality System monitoring data, Warren County's air is good on balance, cleaner than the median US county, a median AQI of 35 with 78.7% of 150 monitored days in the Good band, driven mainly by Ozone.
- 35
- median AQI · Good
- 78.7%
- days rated Good
- Ozone
- main pollutant
- 52%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 138.
Data updated August 2026
- Good · 118 d · 78.7%
- Moderate · 29 d · 19.3%
- USG · 3 d · 2.0%
How did Warren County's air break down in 2025?
Across 150 monitored days, 118 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 138 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 150 days monitored. Median AQI: 35 (Good).
Insights: Warren County, Pennsylvania. EPA monitors recorded a median Air Quality Index of 35 across 150 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 118 (79%) fell in the Good band (AQI 0–50), 29 (19%) registered Moderate readings, and 3 (2%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 58, while the worst single-day peak hit 138 (USG). Residents averaged about 23.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (92 days), PM2.5 (58 days). Across the 2025–2025 trend window, the share of monitored days rated Good shifted by an amount the record cannot support and the median AQI moved +0 points, placing the multi-year trajectory at tracked. The worst single reading over the 2025–2025 window was AQI 138, usg but never Unhealthy. Nearby counties show comparable readings: Adams (74.4% good, AQI 42); Allegheny (46.0% good, AQI 52); Armstrong (70.5% good, AQI 41); Beaver (55.6% good, AQI 46); Berks (68.2% good, AQI 43); Blair (76.9% good, AQI 40).
Air Quality Summary
Good Days
78.7%
118 of 150 monitored days
3.7pp vs 75% target
Max AQI Recorded
138
USG
Health Grade
Good
90th-pct AQI 58
Warren County, Good days share 78.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Warren 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 150 monitored days across EPA AQI categories.
Good
118
79%
Moderate
29
19%
USG
3
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 Warren County.
- Ozone · 92 days · 61.3%
- PM2.5 · 58 days · 38.7%
Health Impact Assessment
Good
Warren County's air quality is rated Good based on 78.7% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 78.7% of monitored days in 2025, with a median AQI of 35. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 92 of 150 monitored days.
How does Warren County compare?
How Warren County compares
Good-day share better than US avg
Warren County 78.7%
Atascosa County, Texas 76.0%
US average 76.0%
Median AQI better than US avg
Warren County 35
Atascosa County, Texas 35
US average 39
Unhealthy days / yr better than US avg
Warren County 0
Atascosa County, Texas 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Warren County (35), not geographic neighbors.
Atascosa County, Texas
Median AQI 35 · 76.0% Good-day share
Benzie County, Michigan
Median AQI 35 · 91.1% Good-day share
Berkeley County, South Carolina
Median AQI 35 · 93.3% Good-day share
Boone County, Indiana
Median AQI 35 · 89.7% Good-day share
Brazoria County, Texas
Median AQI 35 · 80.8% Good-day share
Caroline County, Virginia
Median AQI 35 · 96.7% 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).
Gloucester County, New Jersey
78.7% Good-day share · median AQI 39
Iberville County, Louisiana
78.6% Good-day share · median AQI 40
Ocean County, New Jersey
78.8% Good-day share · median AQI 39
Jessamine County, Kentucky
78.5% Good-day share · median AQI 41
Sheboygan County, Wisconsin
78.9% Good-day share · median AQI 41
Bossier County, Louisiana
78.9% Good-day share · median AQI 42
Pennsylvania counties on the map
Geographic containment only, other monitored counties in Pennsylvania, independent of AQI or pollutant match.
What Warren 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 35 means for exposure. Health guidance
- See how Warren County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Warren County with its Pennsylvania neighbours before drawing a conclusion about the region. All of Pennsylvania
Based on 150 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 Warren County, Pennsylvania? ▼
Warren County has a median Air Quality Index (AQI) of 35, rated "Good." 78.7% of monitored days (118 out of 150) had good air quality in 2025.
What is the main pollutant in Warren County? ▼
The primary pollutant in Warren County is Ozone (O3), which was the main AQI driver on 92 days (61% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Warren County have? ▼
In 2025, Warren County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 138.
Is the air quality in Warren County getting better or worse? ▼
Insufficient trend data is available for Warren County.
What does AQI 35 mean for health? ▼
Warren County's median AQI of 35 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Warren County compare to other counties in Pennsylvania? ▼
Warren County has 78.7% good air days. Nearby counties in Pennsylvania: Adams (74.4% good), Allegheny (46.0% good), Armstrong (70.5% good), Beaver (55.6% good), Berks (68.2% good), Blair (76.9% good).
What is the 90th percentile AQI in Warren County? ▼
The 90th percentile AQI for Warren County is 58, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 138 (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 Warren County, Pennsylvania · 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.