Median AQI
53
Moderate
Indiana · County air quality · 2025
Lake County, Indiana
Median AQI 53 (Moderate). 38.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 53
- Median AQI
- 38.8%
- Good-air days
- 4
- Unhealthy days
- 3%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Lake County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 53 with 38.8% of 273 monitored days in the Good band, driven mainly by PM2.5.
- 53
- median AQI · Moderate
- 38.8%
- days rated Good
- PM2.5
- main pollutant
- 3%
- cleaner than US counties
4 days reached Unhealthy or worse; the worst single reading hit AQI 219.
Data updated July 2026
- Good · 106 d · 38.8%
- Moderate · 152 d · 55.7%
- USG · 11 d · 4.0%
- Unhealthy · 3 d · 1.1%
- Very Unhealthy · 1 d · 0.4%
How did Lake County's air break down in 2025?
Across 273 monitored days, 106 fell in the Good band (AQI 0–50) and 4 reached Unhealthy or worse. The worst single day peaked at AQI 219 (Very Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 53 (Moderate).
Insights: Lake County, Indiana. EPA monitors recorded a median Air Quality Index of 53 across 273 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 106 (39%) fell in the Good band (AQI 0–50), 152 (56%) registered Moderate readings, and 11 (4%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 85, while the worst single-day peak hit 219 (Very Unhealthy). Residents averaged about 11.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (200 days), Ozone (68 days), PM10 (5 days). Across the 2020–2025 trend window, good days shifted by -55 and the median AQI moved +1 points, placing the multi-year trajectory at worsening. Residents and visitors experienced 4 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Allen (58.2% good, AQI 45); Bartholomew (69.2% good, AQI 44); Boone (86.9% good, AQI 38); Brown (94.5% good, AQI 37); Carroll (87.8% good, AQI 37); Clark (59.7% good, AQI 46).
Air Quality Summary
Good Days
38.8%
106 of 273 monitored days
-36.2pp vs 75% target
Max AQI Recorded
219
Very Unhealthy
Health Grade
Poor
90th-pct AQI 85
Lake County, Good days share 38.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Lake County, Unhealthy-or-worse share 1.5%
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 273 monitored days across EPA AQI categories.
Good
106
39%
Moderate
152
56%
USG
11
4%
Unhealthy
3
1%
Very Unhealthy
1
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Lake County.
- PM2.5 · 200 days · 73.3%
- Ozone · 68 days · 24.9%
- PM10 · 5 days · 1.8%
Health Impact Assessment
Poor
Lake County's air quality is rated Poor based on 38.8% good air days. There were 4 unhealthy days in 2025 when outdoor activity should be limited.
Air quality reached unhealthy levels on 4 days in 2025 (3 Unhealthy, 1 Very Unhealthy). Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, and adults over 65, should review the daily breakdown below and follow local air-quality advisories on high-AQI days.
Sensitive group advisory
People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.
The dominant pollutant is PM2.5, driving AQI on 200 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Lake County. Best year: 2024 (162 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 161 | 199 | 6 | 0 | 52 | 136 |
| 2021 | 134 | 225 | 5 | 1 | 54 | 175 |
| 2022 | 152 | 208 | 5 | 0 | 52 | 143 |
| 2023 | 125 | 222 | 16 | 1 | 55 | 215 |
| 2024 | 162 | 199 | 4 | 1 | 52 | 166 |
| 2025 | 106 | 152 | 11 | 3 | 53 | 219 |
How does Lake County compare?
How Lake County compares
Good-day share worse than US avg
Lake County 38.8%
Allen County, Indiana 58.2%
US average 76.5%
Median AQI worse than US avg
Lake County 53
Allen County, Indiana 45
US average 38
Unhealthy days / yr worse than US avg
Lake County 4
Allen County, Indiana 0
US average 0
Other Counties in Indiana
Air quality comparison for nearby counties in Indiana.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Lake County.
Bexar County, Texas
AQI 53 · 39.8% good
Cook County, Illinois
AQI 53 · 40.5% good
Cuyahoga County, Ohio
AQI 53 · 43.6% good
Dallas County, Texas
AQI 53 · 41.0% good
Jefferson County, Alabama
AQI 53 · 36.8% good
Kings County, California
AQI 53 · 39.8% good
What Lake County's air means for you
On most days the air here is fine, but PM2.5 drives 4 unhealthy-or-worse days a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 53 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 Indiana neighbours before drawing a conclusion about the region. All of Indiana
Based on 273 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 Lake County, Indiana? ▼
Lake County has a median Air Quality Index (AQI) of 53, rated "Moderate." 38.8% of monitored days (106 out of 273) had good air quality in 2025.
What is the main pollutant in Lake County? ▼
The primary pollutant in Lake County is Fine Particles (PM2.5), which was the main AQI driver on 200 days (73% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Lake County have? ▼
In 2025, Lake County recorded 4 unhealthy air days (3 Unhealthy, 1 Very Unhealthy, 0 Hazardous). The maximum AQI reached 219.
Is the air quality in Lake County getting better or worse? ▼
Air quality in Lake County is worsening based on 5-year trends (2020-2025). Best year: 2024 with 162 good days. Worst year: 2025 with 106 good days.
What does AQI 53 mean for health? ▼
Lake County's median AQI of 53 falls in the "Moderate" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Lake County compare to other counties in Indiana? ▼
Lake County has 38.8% good air days. Nearby counties in Indiana: Allen (58.2% good), Bartholomew (69.2% good), Boone (86.9% good), Brown (94.5% good), Carroll (87.8% good), Clark (59.7% good).
What is the 90th percentile AQI in Lake County? ▼
The 90th percentile AQI for Lake County is 85, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 219 (Very Unhealthy).
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.