Median AQI
43
Good
Ohio · County air quality · 2025
Clermont County, Ohio
Median AQI 43 (Good). 72.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 43
- Median AQI
- 72.1%
- Good-air days
- 0
- Unhealthy days
- 35%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Clermont County's air is good on balance, more polluted than the median US county, a median AQI of 43 with 72.1% of 272 monitored days in the Good band, driven mainly by Ozone.
- 43
- median AQI · Good
- 72.1%
- days rated Good
- Ozone
- main pollutant
- 35%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 119.
Data updated July 2026
- Good · 196 d · 72.1%
- Moderate · 73 d · 26.8%
- USG · 3 d · 1.1%
How did Clermont County's air break down in 2025?
Across 272 monitored days, 196 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 119 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 272 days monitored. Median AQI: 43 (Good).
Insights: Clermont County, Ohio. EPA monitors recorded a median Air Quality Index of 43 across 272 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 196 (72%) fell in the Good band (AQI 0–50), 73 (27%) registered Moderate readings, and 3 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 61, while the worst single-day peak hit 119 (USG). Residents averaged about 21.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (147 days), PM2.5 (125 days). Across the 2020–2025 trend window, good days shifted by -100 and the median AQI moved +4 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 119, usg but never Unhealthy. Nearby counties show comparable readings: Allen (65.9% good, AQI 43); Ashtabula (81.2% good, AQI 43); Athens (80.3% good, AQI 33); Belmont (63.0% good, AQI 42); Butler (33.3% good, AQI 55); Clark (59.4% good, AQI 46).
Air Quality Summary
Good Days
72.1%
196 of 272 monitored days
-2.9pp vs 75% target
Max AQI Recorded
119
USG
Health Grade
Moderate
90th-pct AQI 61
Clermont County, Good days share 72.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Clermont 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 272 monitored days across EPA AQI categories.
Good
196
72%
Moderate
73
27%
USG
3
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 Clermont County.
- Ozone · 147 days · 54.0%
- PM2.5 · 125 days · 46.0%
Health Impact Assessment
Moderate
Clermont County's air quality is rated Moderate based on 72.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 72.1% of monitored days in 2025, with a median AQI of 43. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 147 of 272 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Clermont County. Best year: 2024 (305 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 296 | 65 | 0 | 0 | 39 | 100 |
| 2021 | 263 | 101 | 0 | 0 | 42 | 97 |
| 2022 | 238 | 121 | 1 | 0 | 44 | 129 |
| 2023 | 279 | 74 | 4 | 1 | 41 | 175 |
| 2024 | 305 | 52 | 3 | 0 | 39 | 119 |
| 2025 | 196 | 73 | 3 | 0 | 43 | 119 |
How does Clermont County compare?
How Clermont County compares
Good-day share worse than US avg
Clermont County 72.1%
Allen County, Ohio 65.9%
US average 76.5%
Median AQI worse than US avg
Clermont County 43
Allen County, Ohio 43
US average 38
Unhealthy days / yr about average
Clermont County 0
Allen County, Ohio 0
US average 0
Other Counties in Ohio
Air quality comparison for nearby counties in Ohio.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Clermont County.
Allegan County, Michigan
AQI 43 · 71.2% good
Allen County, Ohio
AQI 43 · 65.9% good
Ashtabula County, Ohio
AQI 43 · 81.2% good
Bell County, Kentucky
AQI 43 · 63.5% good
Boise County, Idaho
AQI 43 · 72.9% good
Brazos County, Texas
AQI 43 · 63.4% good
What Clermont 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 43 means for exposure. Health guidance
- See how Clermont County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Clermont County with its Ohio neighbours before drawing a conclusion about the region. All of Ohio
Based on 272 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 Clermont County, Ohio? ▼
Clermont County has a median Air Quality Index (AQI) of 43, rated "Good." 72.1% of monitored days (196 out of 272) had good air quality in 2025.
What is the main pollutant in Clermont County? ▼
The primary pollutant in Clermont County is Ozone (O3), which was the main AQI driver on 147 days (54% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Clermont County have? ▼
In 2025, Clermont County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 119.
Is the air quality in Clermont County getting better or worse? ▼
Air quality in Clermont County is worsening based on 5-year trends (2020-2025). Best year: 2024 with 305 good days. Worst year: 2025 with 196 good days.
What does AQI 43 mean for health? ▼
Clermont County's median AQI of 43 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 Clermont County compare to other counties in Ohio? ▼
Clermont County has 72.1% good air days. Nearby counties in Ohio: Allen (65.9% good), Ashtabula (81.2% good), Athens (80.3% good), Belmont (63.0% good), Butler (33.3% good), Clark (59.4% good).
What is the 90th percentile AQI in Clermont County? ▼
The 90th percentile AQI for Clermont County is 61, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 119 (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.