Median AQI
55
Moderate
Texas · County air quality · 2025
Montgomery County, Texas
Median AQI 55 (Moderate). 30.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 55
- Median AQI
- 30.7%
- Good-air days
- 0
- Unhealthy days
- 1%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Montgomery County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 55 with 30.7% of 241 monitored days in the Good band, driven mainly by PM2.5.
- 55
- median AQI · Moderate
- 30.7%
- days rated Good
- PM2.5
- main pollutant
- 1%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 133.
Data updated July 2026
- Good · 74 d · 30.7%
- Moderate · 160 d · 66.4%
- USG · 7 d · 2.9%
How did Montgomery County's air break down in 2025?
Across 241 monitored days, 74 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 133 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 241 days monitored. Median AQI: 55 (Moderate).
Insights: Montgomery County, Texas. EPA monitors recorded a median Air Quality Index of 55 across 241 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 74 (31%) fell in the Good band (AQI 0–50), 160 (66%) registered Moderate readings, and 7 (3%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 67, while the worst single-day peak hit 133 (USG). Residents averaged about 9.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (179 days), Ozone (62 days). Across the 2020–2025 trend window, good days shifted by -145 and the median AQI moved +11 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 133, 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
30.7%
74 of 241 monitored days
-44.3pp vs 75% target
Max AQI Recorded
133
USG
Health Grade
Poor
90th-pct AQI 67
Montgomery County, Good days share 30.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Montgomery 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 241 monitored days across EPA AQI categories.
Good
74
31%
Moderate
160
66%
USG
7
3%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Montgomery County.
- PM2.5 · 179 days · 74.3%
- Ozone · 62 days · 25.7%
Health Impact Assessment
Poor
Montgomery County's air quality is rated Poor based on 30.7% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 30.7% of monitored days in 2025, with a median AQI of 55. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 179 of 241 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Montgomery County. Best year: 2020 (219 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 219 | 139 | 8 | 0 | 44 | 129 |
| 2021 | 204 | 152 | 2 | 1 | 47 | 151 |
| 2022 | 175 | 183 | 6 | 0 | 51 | 126 |
| 2023 | 151 | 204 | 9 | 0 | 53 | 122 |
| 2024 | 111 | 231 | 20 | 1 | 55 | 166 |
| 2025 | 74 | 160 | 7 | 0 | 55 | 133 |
How does Montgomery County compare?
How Montgomery County compares
Good-day share worse than US avg
Montgomery County 30.7%
Atascosa County, Texas 58.0%
US average 76.5%
Median AQI worse than US avg
Montgomery County 55
Atascosa County, Texas 45
US average 38
Unhealthy days / yr about average
Montgomery 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 Montgomery County.
Butler County, Ohio
AQI 55 · 33.3% good
Cameron County, Texas
AQI 55 · 31.7% good
Nueces County, Texas
AQI 55 · 35.0% good
Pima County, Arizona
AQI 55 · 37.0% good
Denver County, Colorado
AQI 54 · 44.2% good
Franklin County, Ohio
AQI 54 · 39.8% good
What Montgomery 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 55 means for exposure. Health guidance
- See how Montgomery County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Montgomery County with its Texas neighbours before drawing a conclusion about the region. All of Texas
Based on 241 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 Montgomery County, Texas? ▼
Montgomery County has a median Air Quality Index (AQI) of 55, rated "Moderate." 30.7% of monitored days (74 out of 241) had good air quality in 2025.
What is the main pollutant in Montgomery County? ▼
The primary pollutant in Montgomery County is Fine Particles (PM2.5), which was the main AQI driver on 179 days (74% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Montgomery County have? ▼
In 2025, Montgomery County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 133.
Is the air quality in Montgomery County getting better or worse? ▼
Air quality in Montgomery County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 219 good days. Worst year: 2025 with 74 good days.
What does AQI 55 mean for health? ▼
Montgomery County's median AQI of 55 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 Montgomery County compare to other counties in Texas? ▼
Montgomery County has 30.7% 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 Montgomery County? ▼
The 90th percentile AQI for Montgomery County is 67, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 133 (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.