Median AQI
45
Good
Texas · County air quality · 2025
Harrison County, Texas
Median AQI 45 (Good). 62.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 45
- Median AQI
- 62.1%
- Good-air days
- 0
- Unhealthy days
- 18%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Harrison County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 45 with 62.1% of 243 monitored days in the Good band, driven mainly by PM2.5.
- 45
- median AQI · Good
- 62.1%
- days rated Good
- PM2.5
- main pollutant
- 18%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 100.
Data updated July 2026
- Good · 151 d · 62.1%
- Moderate · 92 d · 37.9%
How did Harrison County's air break down in 2025?
Across 243 monitored days, 151 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 100 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 243 days monitored. Median AQI: 45 (Good).
Insights: Harrison County, Texas. EPA monitors recorded a median Air Quality Index of 45 across 243 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 151 (62%) fell in the Good band (AQI 0–50), 92 (38%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 59, while the worst single-day peak hit 100 (Moderate). Residents averaged about 18.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (165 days), Ozone (78 days). Across the 2020–2025 trend window, good days shifted by -113 and the median AQI moved +5 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 100, moderate 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
62.1%
151 of 243 monitored days
-12.9pp vs 75% target
Max AQI Recorded
100
Moderate
Health Grade
Moderate
90th-pct AQI 59
Harrison County, Good days share 62.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Harrison 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 243 monitored days across EPA AQI categories.
Good
151
62%
Moderate
92
38%
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 Harrison County.
- PM2.5 · 165 days · 67.9%
- Ozone · 78 days · 32.1%
Health Impact Assessment
Moderate
Harrison County's air quality is rated Moderate based on 62.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 62.1% of monitored days in 2025, with a median AQI of 45. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 165 of 243 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Harrison County. Best year: 2020 (264 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 264 | 99 | 0 | 0 | 40 | 100 |
| 2021 | 205 | 153 | 3 | 1 | 47 | 161 |
| 2022 | 164 | 159 | 4 | 1 | 51 | 181 |
| 2023 | 207 | 151 | 1 | 0 | 47 | 111 |
| 2024 | 233 | 129 | 0 | 1 | 44 | 263 |
| 2025 | 151 | 92 | 0 | 0 | 45 | 100 |
How does Harrison County compare?
How Harrison County compares
Good-day share worse than US avg
Harrison County 62.1%
Atascosa County, Texas 58.0%
US average 76.5%
Median AQI worse than US avg
Harrison County 45
Atascosa County, Texas 45
US average 38
Unhealthy days / yr about average
Harrison 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 Harrison County.
Adair County, Oklahoma
AQI 45 · 59.2% good
Allen County, Indiana
AQI 45 · 58.2% good
Atascosa County, Texas
AQI 45 · 58.0% good
Baker County, Florida
AQI 45 · 69.1% good
Carson City County, Nevada
AQI 45 · 79.3% good
Clinton County, Iowa
AQI 45 · 59.9% good
What Harrison 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 45 means for exposure. Health guidance
- See how Harrison County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Harrison County with its Texas neighbours before drawing a conclusion about the region. All of Texas
Based on 243 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 Harrison County, Texas? ▼
Harrison County has a median Air Quality Index (AQI) of 45, rated "Good." 62.1% of monitored days (151 out of 243) had good air quality in 2025.
What is the main pollutant in Harrison County? ▼
The primary pollutant in Harrison County is Fine Particles (PM2.5), which was the main AQI driver on 165 days (68% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Harrison County have? ▼
In 2025, Harrison County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 100.
Is the air quality in Harrison County getting better or worse? ▼
Air quality in Harrison County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 264 good days. Worst year: 2025 with 151 good days.
What does AQI 45 mean for health? ▼
Harrison County's median AQI of 45 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 Harrison County compare to other counties in Texas? ▼
Harrison County has 62.1% 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 Harrison County? ▼
The 90th percentile AQI for Harrison County is 59, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 100 (Moderate).
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.