Median AQI
52
Moderate
Texas · County air quality · 2025
McLennan County, Texas
Median AQI 52 (Moderate). 43.4% of monitored days rated Good, direct from EPA Air Quality System stations.
- 52
- Median AQI
- 43.4%
- Good-air days
- 0
- Unhealthy days
- 4%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, McLennan County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 52 with 43.4% of 244 monitored days in the Good band, driven mainly by PM2.5.
- 52
- median AQI · Moderate
- 43.4%
- days rated Good
- PM2.5
- main pollutant
- 4%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 142.
Data updated July 2026
- Good · 106 d · 43.4%
- Moderate · 135 d · 55.3%
- USG · 3 d · 1.2%
How did McLennan County's air break down in 2025?
Across 244 monitored days, 106 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 142 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 244 days monitored. Median AQI: 52 (Moderate).
Insights: McLennan County, Texas. EPA monitors recorded a median Air Quality Index of 52 across 244 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 106 (43%) fell in the Good band (AQI 0–50), 135 (55%) registered Moderate readings, and 3 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 67, while the worst single-day peak hit 142 (USG). Residents averaged about 13.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (170 days), Ozone (70 days), CO (4 days). Across the 2020–2025 trend window, good days shifted by -188 and the median AQI moved +13 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 142, usg 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
43.4%
106 of 244 monitored days
-31.6pp vs 75% target
Max AQI Recorded
142
USG
Health Grade
Poor
90th-pct AQI 67
McLennan County, Good days share 43.4%
National avg
Share of monitored days at AQI 0-50 (Good band).
McLennan 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 244 monitored days across EPA AQI categories.
Good
106
43%
Moderate
135
55%
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 McLennan County.
- PM2.5 · 170 days · 69.7%
- Ozone · 70 days · 28.7%
- CO · 4 days · 1.6%
Health Impact Assessment
Poor
McLennan County's air quality is rated Poor based on 43.4% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 43.4% of monitored days in 2025, with a median AQI of 52. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 170 of 244 monitored days.
5-Year Air Quality Trend
Air quality is worsening in McLennan County. Best year: 2020 (294 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 294 | 72 | 0 | 0 | 39 | 97 |
| 2021 | 280 | 84 | 0 | 0 | 39 | 100 |
| 2022 | 209 | 155 | 0 | 0 | 48 | 100 |
| 2023 | 169 | 188 | 8 | 0 | 52 | 129 |
| 2024 | 126 | 234 | 5 | 0 | 53 | 133 |
| 2025 | 106 | 135 | 3 | 0 | 52 | 142 |
How does McLennan County compare?
How McLennan County compares
Good-day share worse than US avg
McLennan County 43.4%
Atascosa County, Texas 58.0%
US average 76.5%
Median AQI worse than US avg
McLennan County 52
Atascosa County, Texas 45
US average 38
Unhealthy days / yr about average
McLennan 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 McLennan County.
Duval County, Florida
AQI 52 · 40.7% good
Hinds County, Mississippi
AQI 52 · 43.4% good
Jefferson County, Texas
AQI 52 · 42.4% good
Orange County, California
AQI 52 · 44.5% good
Union County, Arkansas
AQI 52 · 44.0% good
Wayne County, Michigan
AQI 52 · 46.4% good
What McLennan County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 52 means for exposure. Health guidance
- See how McLennan County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare McLennan County with its Texas neighbours before drawing a conclusion about the region. All of Texas
Based on 244 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 McLennan County, Texas? ▼
McLennan County has a median Air Quality Index (AQI) of 52, rated "Moderate." 43.4% of monitored days (106 out of 244) had good air quality in 2025.
What is the main pollutant in McLennan County? ▼
The primary pollutant in McLennan County is Fine Particles (PM2.5), which was the main AQI driver on 170 days (70% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does McLennan County have? ▼
In 2025, McLennan County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 142.
Is the air quality in McLennan County getting better or worse? ▼
Air quality in McLennan County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 294 good days. Worst year: 2025 with 106 good days.
What does AQI 52 mean for health? ▼
McLennan County's median AQI of 52 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 McLennan County compare to other counties in Texas? ▼
McLennan County has 43.4% 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 McLennan County? ▼
The 90th percentile AQI for McLennan County is 67, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 142 (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.