Texas · County air quality · 2025
Montgomery County, Texas
Median AQI 53 (Moderate). 39.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 53
- Median AQI
- 39.1%
- Good-air days
- 0
- Unhealthy days
- 3%
- Cleaner than US counties
Montgomery County's 2025 annual median AQI is 53 (Moderate), with 39.1% Good days
According to the U.S. EPA Air Quality System, Montgomery County, Texas posted a 2025 median AQI of 53 (Moderate) across 363 monitored days, with 39.1% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Montgomery County's 39.1% Good-day share places it cleaner than 3% of US counties in 2025.
- Closest median-AQI peer
- Cook County (40.8% Good, median AQI 53) is the closest nationwide median-AQI peer to Montgomery County.
- 2020–2025 trend
- Montgomery County's floor-qualifying Good-day share is worsening from 2020 to 2025 (59.8% → 39.1%).
- Median AQI
- Median AQI: 53
According to the 2025 EPA AQS county release on PlainAirData, Montgomery County, Texas ranks #916 of 951 by median AQI (53) and #924 by good-day share (39.1%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.
Annual release change
What changed in the 2025 EPA annual release
- Montgomery County's Good-day share rose from 30.6% to 39.1% between the 2024 and 2025 EPA annual releases, a change of +8.5 percentage points.
- Montgomery County's peak single-day AQI fell from 166 to 133 between the 2024 and 2025 EPA annual releases, a change of -33 points.
- Montgomery County's Unhealthy-category days fell from 1 to 0 between the 2024 and 2025 EPA annual releases, a change of -1 days.
Data updated August 2026
- Good · 142 d · 39.1%
- Moderate · 213 d · 58.7%
- USG · 8 d · 2.2%
How did Montgomery County's air break down in 2025?
Across 363 monitored days, 142 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 →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Montgomery County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Montgomery County's Good-day share is 39.1% - cleaner than 3% of that comparison set.
Montgomery County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
39.1% 3rd percentile higher than 3% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Montgomery County.
- PM2.5 · 242 days · 66.7%
- Ozone · 121 days · 33.3%
2024 daily-monitor rhythm in Montgomery County
Month-by-month median AQI from EPA day-level county monitors (363 reported days in 2024). Aug posted the highest typical readings (median AQI 64, peak 140); Jan was cleanest at median 45. Summer months (Jun–Aug) averaged median AQI 62 vs 50 in Dec–Feb. 1 day crossed Unhealthy (AQI >150) at least once that year.
Five-year seasonal record
EPA day-level county files · 2020–20241,816 daily readings show a recurring local pattern: Jun has the highest matched-month median AQI (55), while Jan is lowest (41). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Montgomery County's air quality is rated Poor based on 39.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 39.1% of monitored days in 2025, with a median AQI of 53. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 242 of 363 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Montgomery County. Highest Good-day share: 2020 (59.8%, 219 of 366 monitored 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 | 142 | 213 | 8 | 0 | 53 | 133 |
How does Montgomery County compare?
How Montgomery County compares
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Montgomery County, Texas · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData 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.