Median AQI
42
Good
Ohio · County air quality · 2025
Lake County, Ohio
Median AQI 42 (Good). 67.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 42
- Median AQI
- 67.2%
- Good-air days
- 0
- Unhealthy days
- 26%
- Cleaner than US counties
Lake County's 2025 annual median AQI is 42 (Good), with 67.2% Good days
According to the U.S. EPA Air Quality System, Lake County, Ohio posted a 2025 median AQI of 42 (Good) across 363 monitored days, with 67.2% 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
- Lake County's 67.2% Good-day share places it cleaner than 26% of US counties in 2025.
- Closest median-AQI peer
- Ada County (74.0% Good, median AQI 42) is the closest nationwide median-AQI peer to Lake County.
- 2020–2025 trend
- Lake County's floor-qualifying Good-day share is worsening from 2020 to 2025 (80.9% → 67.2%).
- Median AQI
- Median AQI: 42
The verdict
According to EPA Air Quality System monitoring data, Lake County's air is good on balance, more polluted than the median US county, a median AQI of 42 with 67.2% of 363 monitored days in the Good band, driven mainly by Ozone.
- 42
- median AQI · Good
- 67.2%
- days rated Good
- Ozone
- main pollutant
- 26%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 133.
Annual release change
What changed in the 2025 EPA annual release
- Lake County's Good-day share fell from 74.5% to 67.2% between the 2024 and 2025 EPA annual releases, a change of -7.3 percentage points.
Data updated August 2026
- Good · 244 d · 67.2%
- Moderate · 114 d · 31.4%
- USG · 5 d · 1.4%
How did Lake County's air break down in 2025?
Across 363 monitored days, 244 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 133 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 363 days monitored. Median AQI: 42 (Good).
Insights: Lake County, Ohio. EPA monitors recorded a median Air Quality Index of 42 across 363 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 244 (67%) fell in the Good band (AQI 0–50), 114 (31%) registered Moderate readings, and 5 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 71, while the worst single-day peak hit 133 (USG). Residents averaged about 20.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (198 days), PM2.5 (165 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -13.7 points and the median AQI moved +2 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 133, usg but never Unhealthy. Nearby counties show comparable readings: Allen (67.0% good, AQI 42); Ashtabula (81.2% good, AQI 43); Athens (83.4% good, AQI 31); Belmont (63.0% good, AQI 42); Butler (33.1% good, AQI 55); Clark (61.4% good, AQI 45).
Air Quality Summary
Good Days
67.2%
244 of 363 monitored days
-7.8pp vs 75% target
Max AQI Recorded
133
USG
Health Grade
Moderate
90th-pct AQI 71
Lake County, Good days share 67.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Lake 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 363 monitored days across EPA AQI categories.
Good
244
67%
Moderate
114
31%
USG
5
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 Lake County.
- Ozone · 198 days · 54.5%
- PM2.5 · 165 days · 45.5%
Health Impact Assessment
Moderate
Lake County's air quality is rated Moderate based on 67.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 67.2% of monitored days in 2025, with a median AQI of 42. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 198 of 363 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Lake County. Highest Good-day share: 2020 (80.9%, 296 of 366 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 296 | 64 | 6 | 0 | 40 | 140 |
| 2021 | 251 | 107 | 7 | 0 | 41 | 122 |
| 2022 | 281 | 80 | 4 | 0 | 41 | 150 |
| 2023 | 259 | 96 | 7 | 3 | 42 | 170 |
| 2024 | 272 | 89 | 4 | 0 | 41 | 136 |
| 2025 | 244 | 114 | 5 | 0 | 42 | 133 |
How does Lake County compare?
How Lake County compares
Good-day share worse than US avg
Lake County 67.2%
Ada County, Idaho 74.0%
US average 76.0%
Median AQI worse than US avg
Lake County 42
Ada County, Idaho 42
US average 39
Unhealthy days / yr better than US avg
Lake County 0
Ada County, Idaho 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Lake County (42), not geographic neighbors.
Ada County, Idaho
Median AQI 42 · 74.0% Good-day share
Adams County, Pennsylvania
Median AQI 42 · 74.4% Good-day share
Allen County, Ohio
Median AQI 42 · 67.0% Good-day share
Asotin County, Washington
Median AQI 42 · 61.9% Good-day share
Baldwin County, Alabama
Median AQI 42 · 75.5% Good-day share
Bell County, Kentucky
Median AQI 42 · 67.0% 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).
New Haven County, Connecticut
67.1% Good-day share · median AQI 43
Douglas County, Colorado
67.7% Good-day share · median AQI 46
Preble County, Ohio
67.7% Good-day share · median AQI 43
Washington County, Pennsylvania
67.7% Good-day share · median AQI 44
Comanche County, Oklahoma
66.8% Good-day share · median AQI 44
Warren County, Ohio
67.9% Good-day share · median AQI 44
Ohio counties on the map
Geographic containment only, other monitored counties in Ohio, independent of AQI or pollutant match.
What Lake 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 42 means for exposure. Health guidance
- See how Lake County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Lake County with its Ohio neighbours before drawing a conclusion about the region. All of Ohio
Based on 363 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 Lake County, Ohio? ▼
Lake County has a median Air Quality Index (AQI) of 42, rated "Good." 67.2% of monitored days (244 out of 363) had good air quality in 2025.
What is the main pollutant in Lake County? ▼
The primary pollutant in Lake County is Ozone (O3), which was the main AQI driver on 198 days (55% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Lake County have? ▼
In 2025, Lake County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 133.
Is the air quality in Lake County getting better or worse? ▼
Air quality in Lake County is worsening across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2020 at 80.9% (296 of 366 days). Lowest qualifying Good-day share: 2025 at 67.2% (244 of 363 days).
What does AQI 42 mean for health? ▼
Lake County's median AQI of 42 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Lake County compare to other counties in Ohio? ▼
Lake County has 67.2% good air days. Nearby counties in Ohio: Allen (67.0% good), Ashtabula (81.2% good), Athens (83.4% good), Belmont (63.0% good), Butler (33.1% good), Clark (61.4% good).
What is the 90th percentile AQI in Lake County? ▼
The 90th percentile AQI for Lake County is 71, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 133 (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 Lake County, Ohio · 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.