Texas · County air quality · 2025
Harris County, Texas
Median AQI 62 (Moderate). 11.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 62
- Median AQI
- 11.0%
- Good-air days
- 10
- Unhealthy days
- 0%
- Cleaner than US counties
Harris County's 2025 annual median AQI is 62 (Moderate), with 11.0% Good days
According to the U.S. EPA Air Quality System, Harris County, Texas posted a 2025 median AQI of 62 (Moderate) across 365 monitored days, with 11.0% rated Good and 10 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Harris County's 11.0% Good-day share places it cleaner than 0% of US counties in 2025.
- Closest median-AQI peer
- Clark County (31.0% Good, median AQI 61) is the closest nationwide median-AQI peer to Harris County.
- 2020–2025 trend
- Harris County's floor-qualifying Good-day share is worsening from 2020 to 2025 (29.8% → 11.0%).
- Median AQI
- Median AQI: 62
According to the 2025 EPA AQS county release on PlainAirData, Harris County, Texas ranks #941 of 951 by median AQI (62) and #948 by good-day share (11.0%). 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
- Harris County's Unhealthy-category days fell from 13 to 10 between the 2024 and 2025 EPA annual releases, a change of -3 days.
- Harris County's peak single-day AQI fell from 201 to 172 between the 2024 and 2025 EPA annual releases, a change of -29 points.
- Harris County's Good-day share fell from 13.7% to 11.0% between the 2024 and 2025 EPA annual releases, a change of -2.7 percentage points.
Data updated August 2026
- Good · 40 d · 11.0%
- Moderate · 287 d · 78.6%
- USG · 28 d · 7.7%
- Unhealthy · 10 d · 2.7%
How did Harris County's air break down in 2025?
Across 365 monitored days, 40 fell in the Good band (AQI 0–50) and 10 reached Unhealthy or worse. The worst single day peaked at AQI 172 (Unhealthy).
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 Harris County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Harris County's Good-day share is 11.0% - cleaner than 0% of that comparison set.
Harris County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
11.0% 0th percentile higher than 0% 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 Harris County.
- PM2.5 · 241 days · 66.0%
- Ozone · 99 days · 27.1%
- PM10 · 24 days · 6.6%
- NO₂ · 1 days · 0.3%
2024 daily-monitor rhythm in Harris County
Month-by-month median AQI from EPA day-level county monitors (366 reported days in 2024). Aug posted the highest typical readings (median AQI 93, peak 200); Jan was cleanest at median 56. Summer months (Jun–Aug) averaged median AQI 75 vs 57 in Dec–Feb. 14 days crossed Unhealthy (AQI >150) at least once that year.
Five-year seasonal record
EPA day-level county files · 2020–20241,827 daily readings show a recurring local pattern: Aug has the highest matched-month median AQI (73), while Jan is lowest (56). 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
Harris County's air quality is rated Very Poor based on 11.0% good air days. There were 10 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 28 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 172. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 241 of 365 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Harris County. Highest Good-day share: 2020 (29.8%, 109 of 366 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 109 | 240 | 15 | 2 | 56 | 190 |
| 2021 | 64 | 276 | 18 | 7 | 58 | 179 |
| 2022 | 57 | 281 | 22 | 5 | 60 | 179 |
| 2023 | 44 | 273 | 38 | 9 | 64 | 205 |
| 2024 | 50 | 269 | 33 | 13 | 61 | 201 |
| 2025 | 40 | 287 | 28 | 10 | 62 | 172 |
How does Harris County compare?
How Harris 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 Harris 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.