Median AQI
35
Good
Texas · County air quality · 2025
Smith County, Texas
Median AQI 35 (Good). 92.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 35
- Median AQI
- 92.2%
- Good-air days
- 0
- Unhealthy days
- 81%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Smith County's air is good on balance, cleaner than most US counties, a median AQI of 35 with 92.2% of 243 monitored days in the Good band, driven mainly by Ozone.
- 35
- median AQI · Good
- 92.2%
- days rated Good
- Ozone
- main pollutant
- 81%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 93.
Data updated July 2026
- Good · 224 d · 92.2%
- Moderate · 19 d · 7.8%
How did Smith County's air break down in 2025?
Across 243 monitored days, 224 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 93 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 243 days monitored. Median AQI: 35 (Good).
Insights: Smith County, Texas. EPA monitors recorded a median Air Quality Index of 35 across 243 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 224 (92%) fell in the Good band (AQI 0–50), 19 (8%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 50, while the worst single-day peak hit 93 (Moderate). Residents averaged about 27.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (235 days), NO2 (8 days). Across the 2020–2025 trend window, good days shifted by -128 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 93, 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
92.2%
224 of 243 monitored days
17.2pp vs 75% target
Max AQI Recorded
93
Moderate
Health Grade
Excellent
90th-pct AQI 50
Smith County, Good days share 92.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Smith 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
224
92%
Moderate
19
8%
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 Smith County.
- Ozone · 235 days · 96.7%
- NO₂ · 8 days · 3.3%
Health Impact Assessment
Excellent
Smith County's air quality is rated Excellent based on 92.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 92.2% of monitored days in 2025, with a median AQI of 35. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 235 of 243 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Smith County. Best year: 2020 (352 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 352 | 14 | 0 | 0 | 33 | 84 |
| 2021 | 333 | 28 | 0 | 0 | 35 | 100 |
| 2022 | 289 | 68 | 6 | 0 | 40 | 122 |
| 2023 | 296 | 64 | 4 | 0 | 38 | 119 |
| 2024 | 314 | 48 | 1 | 0 | 39 | 105 |
| 2025 | 224 | 19 | 0 | 0 | 35 | 93 |
How does Smith County compare?
How Smith County compares
Good-day share better than US avg
Smith County 92.2%
Atascosa County, Texas 58.0%
US average 76.5%
Median AQI better than US avg
Smith County 35
Atascosa County, Texas 45
US average 38
Unhealthy days / yr about average
Smith 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 Smith County.
Androscoggin County, Maine
AQI 35 · 85.5% good
Asotin County, Washington
AQI 35 · 73.8% good
Benton County, Washington
AQI 35 · 88.9% good
Benzie County, Michigan
AQI 35 · 91.1% good
Brooke County, West Virginia
AQI 35 · 79.3% good
Bucks County, Pennsylvania
AQI 35 · 87.5% good
What Smith 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 35 means for exposure. Health guidance
- See how Smith County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Smith 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 Smith County, Texas? ▼
Smith County has a median Air Quality Index (AQI) of 35, rated "Good." 92.2% of monitored days (224 out of 243) had good air quality in 2025.
What is the main pollutant in Smith County? ▼
The primary pollutant in Smith County is Ozone (O3), which was the main AQI driver on 235 days (97% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Smith County have? ▼
In 2025, Smith County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 93.
Is the air quality in Smith County getting better or worse? ▼
Air quality in Smith County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 352 good days. Worst year: 2025 with 224 good days.
What does AQI 35 mean for health? ▼
Smith County's median AQI of 35 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 Smith County compare to other counties in Texas? ▼
Smith County has 92.2% 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 Smith County? ▼
The 90th percentile AQI for Smith County is 50, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 93 (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.