Median AQI
38
Good
New Jersey · County air quality · 2025
Warren County, New Jersey
Median AQI 38 (Good). 78.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 38
- Median AQI
- 78.5%
- Good-air days
- 0
- Unhealthy days
- 48%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Warren County's air is good on balance, more polluted than the median US county, a median AQI of 38 with 78.5% of 177 monitored days in the Good band, driven mainly by Ozone.
- 38
- median AQI · Good
- 78.5%
- days rated Good
- Ozone
- main pollutant
- 48%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 105.
Data updated July 2026
- Good · 139 d · 78.5%
- Moderate · 37 d · 20.9%
- USG · 1 d · 0.6%
How did Warren County's air break down in 2025?
Across 177 monitored days, 139 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 105 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 177 days monitored. Median AQI: 38 (Good).
Insights: Warren County, New Jersey. EPA monitors recorded a median Air Quality Index of 38 across 177 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 139 (79%) fell in the Good band (AQI 0–50), 37 (21%) registered Moderate readings, and 1 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 60, while the worst single-day peak hit 105 (USG). Residents averaged about 23.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (123 days), PM2.5 (49 days), NO2 (5 days). Across the 2020–2025 trend window, good days shifted by -148 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 105, usg but never Unhealthy. Nearby counties show comparable readings: Atlantic (79.6% good, AQI 38); Bergen (71.1% good, AQI 40); Camden (69.4% good, AQI 44); Cumberland (73.0% good, AQI 42); Gloucester (72.4% good, AQI 43); Hudson (74.7% good, AQI 41).
Air Quality Summary
Good Days
78.5%
139 of 177 monitored days
3.5pp vs 75% target
Max AQI Recorded
105
USG
Health Grade
Good
90th-pct AQI 60
Warren County, Good days share 78.5%
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 177 monitored days across EPA AQI categories.
Good
139
79%
Moderate
37
21%
USG
1
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 Warren County.
- Ozone · 123 days · 69.5%
- PM2.5 · 49 days · 27.7%
- NO₂ · 5 days · 2.8%
Health Impact Assessment
Good
Warren County's air quality is rated Good based on 78.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 78.5% 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 123 of 177 monitored days.
5-Year Air Quality Trend
Air quality is stable in Warren County. Best year: 2020 (287 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 287 | 74 | 0 | 0 | 38 | 100 |
| 2021 | 237 | 120 | 1 | 0 | 42 | 136 |
| 2022 | 241 | 122 | 0 | 0 | 43 | 86 |
| 2023 | 241 | 114 | 1 | 5 | 41 | 197 |
| 2024 | 284 | 71 | 2 | 0 | 36 | 108 |
| 2025 | 139 | 37 | 1 | 0 | 38 | 105 |
How does Warren County compare?
How Warren County compares
Good-day share better than US avg
Warren County 78.5%
Atlantic County, New Jersey 79.6%
US average 76.5%
Median AQI about average
Warren County 38
Atlantic County, New Jersey 38
US average 38
Unhealthy days / yr about average
Warren County 0
Atlantic County, New Jersey 0
US average 0
Other Counties in New Jersey
Air quality comparison for nearby counties in New Jersey.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Warren County.
Adams County, Illinois
AQI 38 · 94.4% good
Anoka County, Minnesota
AQI 38 · 82.1% good
Atlantic County, New Jersey
AQI 38 · 79.6% good
Avery County, North Carolina
AQI 38 · 93.9% good
Barnstable County, Massachusetts
AQI 38 · 92.5% good
Bay County, Michigan
AQI 38 · 71.8% good
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 38 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 New Jersey neighbours before drawing a conclusion about the region. All of New Jersey
Based on 177 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 Warren County, New Jersey? ▼
Warren County has a median Air Quality Index (AQI) of 38, rated "Good." 78.5% of monitored days (139 out of 177) 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 123 days (69% 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 105.
Is the air quality in Warren County getting better or worse? ▼
Air quality in Warren County is stable based on 5-year trends (2020-2025). Best year: 2020 with 287 good days. Worst year: 2025 with 139 good days.
What does AQI 38 mean for health? ▼
Warren County's median AQI of 38 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 Warren County compare to other counties in New Jersey? ▼
Warren County has 78.5% good air days. Nearby counties in New Jersey: Atlantic (79.6% good), Bergen (71.1% good), Camden (69.4% good), Cumberland (73.0% good), Gloucester (72.4% good), Hudson (74.7% good).
What is the 90th percentile AQI in Warren County? ▼
The 90th percentile AQI for Warren County is 60, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 105 (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.