Median AQI
4
Good
Texas · County air quality · 2025
Karnes County, Texas
Median AQI 4 (Good). 100.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 4
- Median AQI
- 100.0%
- Good-air days
- 0
- Unhealthy days
- 96%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Karnes County's air is good on balance, among the cleanest 5% of US counties, a median AQI of 4 with 100.0% of 234 monitored days in the Good band, driven mainly by NO2.
- 4
- median AQI · Good
- 100.0%
- days rated Good
- NO2
- main pollutant
- 96%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 32.
Data updated July 2026
- Good · 234 d · 100.0%
How did Karnes County's air break down in 2025?
Across 234 monitored days, 234 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 32 (Good).
EPA AQS →Air quality data from EPA Air Quality System (2025). 234 days monitored. Median AQI: 4 (Good).
Insights: Karnes County, Texas. EPA monitors recorded a median Air Quality Index of 4 across 234 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 234 (100%) fell in the Good band (AQI 0–50), 0 (0%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 13, while the worst single-day peak hit 32 (Good). Residents averaged about 30.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as NO2 (234 days). Across the 2020–2025 trend window, good days shifted by -129 and the median AQI moved -2 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 32, good but never Unhealthy. Nearby counties show comparable readings: Atascosa (58.0% good, AQI 45); Bell (61.3% good, AQI 47); Bexar (39.8% good, AQI 53); Bowie (57.3% good, AQI 47); Brazoria (84.8% good, AQI 33); Brazos (63.4% good, AQI 43).
Air Quality Summary
Good Days
100.0%
234 of 234 monitored days
25.0pp vs 75% target
Max AQI Recorded
32
Good
Health Grade
Excellent
90th-pct AQI 13
Karnes County, Good days share 100.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Karnes 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 234 monitored days across EPA AQI categories.
Good
234
100%
Moderate
0
0%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Karnes County.
- NO₂ · 234 days · 100.0%
Health Impact Assessment
Excellent
Karnes County's air quality is rated Excellent based on 100.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 100.0% of monitored days in 2025, with a median AQI of 4. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is NO2, driving AQI on 234 of 234 monitored days.
5-Year Air Quality Trend
Air quality is stable in Karnes County. Best year: 2021 (364 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 363 | 0 | 0 | 0 | 6 | 32 |
| 2021 | 364 | 0 | 0 | 0 | 6 | 26 |
| 2022 | 349 | 0 | 0 | 0 | 6 | 34 |
| 2023 | 357 | 0 | 0 | 0 | 7 | 29 |
| 2024 | 363 | 0 | 0 | 0 | 7 | 33 |
| 2025 | 234 | 0 | 0 | 0 | 4 | 32 |
How does Karnes County compare?
How Karnes County compares
Good-day share better than US avg
Karnes County 100.0%
Atascosa County, Texas 58.0%
US average 76.5%
Median AQI better than US avg
Karnes County 4
Atascosa County, Texas 45
US average 38
Unhealthy days / yr about average
Karnes County 0
Atascosa County, Texas 0
US average 0
Other Counties in Texas
Air quality comparison for nearby counties in Texas.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Karnes County.
Garfield County, Utah
AQI 4 · 100.0% good
Lake County, Montana
AQI 4 · 100.0% good
Rosebud County, Montana
AQI 4 · 100.0% good
San Juan County, Colorado
AQI 4 · 100.0% good
Wayne County, Utah
AQI 4 · 100.0% good
Caguas County, Puerto Rico
AQI 3 · 94.3% good
What Karnes County's air means for you
The air here stays in the breathable range year-round, with NO2 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-NO2 days, the guide explains what a median of 4 means for exposure. Health guidance
- See how Karnes County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Karnes County with its Texas neighbours before drawing a conclusion about the region. All of Texas
Based on 234 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 Karnes County, Texas? ▼
Karnes County has a median Air Quality Index (AQI) of 4, rated "Good." 100.0% of monitored days (234 out of 234) had good air quality in 2025.
What is the main pollutant in Karnes County? ▼
The primary pollutant in Karnes County is Nitrogen Dioxide (NO2), which was the main AQI driver on 234 days (100% of monitored days). Irritates airways. Long-term exposure linked to respiratory infections.
How many unhealthy air days does Karnes County have? ▼
In 2025, Karnes County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 32.
Is the air quality in Karnes County getting better or worse? ▼
Air quality in Karnes County is stable based on 5-year trends (2020-2025). Best year: 2021 with 364 good days. Worst year: 2025 with 234 good days.
What does AQI 4 mean for health? ▼
Karnes County's median AQI of 4 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 Karnes County compare to other counties in Texas? ▼
Karnes County has 100.0% good air days. Nearby counties in Texas: Atascosa (58.0% good), Bell (61.3% good), Bexar (39.8% good), Bowie (57.3% good), Brazoria (84.8% good), Brazos (63.4% good).
What is the 90th percentile AQI in Karnes County? ▼
The 90th percentile AQI for Karnes County is 13, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 32 (Good).
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.