Texas · County air quality · 2025
Collin County, Texas
Median AQI 40 (Good). 75.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 40
- Median AQI
- 75.8%
- Good-air days
- 3
- Unhealthy days
- 46%
- Cleaner than US counties
Collin County's 2025 annual median AQI is 40 (Good), with 75.8% Good days
According to the U.S. EPA Air Quality System, Collin County, Texas posted a 2025 median AQI of 40 (Good) across 359 monitored days, with 75.8% rated Good and 3 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Collin County's 75.8% Good-day share places it cleaner than 46% of US counties in 2025.
- Closest median-AQI peer
- Anderson County (91.3% Good, median AQI 40) is the closest nationwide median-AQI peer to Collin County.
- 2020–2025 trend
- Collin County's floor-qualifying Good-day share is worsening from 2020 to 2025 (86.8% → 75.8%).
- Median AQI
- Median AQI: 40
According to the 2025 EPA AQS county release on PlainAirData, Collin County, Texas ranks #462 of 951 by median AQI (40) and #513 by good-day share (75.8%). 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
- Collin County's Good-day share fell from 77.5% to 75.8% between the 2024 and 2025 EPA annual releases, a change of -1.8 percentage points.
Data updated August 2026
- Good · 272 d · 75.8%
- Moderate · 64 d · 17.8%
- USG · 20 d · 5.6%
- Unhealthy · 3 d · 0.8%
How did Collin County's air break down in 2025?
Across 359 monitored days, 272 fell in the Good band (AQI 0–50) and 3 reached Unhealthy or worse. The worst single day peaked at AQI 156 (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 Collin County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Collin County's Good-day share is 75.8% - cleaner than 46% of that comparison set.
Collin County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
75.8% 46th percentile higher than 46% 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 Collin County.
- Ozone · 359 days · 100.0%
2024 daily-monitor rhythm in Collin County
Month-by-month median AQI from EPA day-level county monitors (365 reported days in 2024). Aug posted the highest typical readings (median AQI 61, peak 161); Dec was cleanest at median 26. Summer months (Jun–Aug) averaged median AQI 52 vs 29 in Dec–Feb. 3 days crossed Unhealthy (AQI >150) at least once that year.
Five-year seasonal record
EPA day-level county files · 2020–20241,802 daily readings show a recurring local pattern: Aug has the highest matched-month median AQI (52), while Dec is lowest (27). 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
Collin County's air quality is rated Good based on 75.8% good air days. There were 3 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 20 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 156. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 359 of 359 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Collin County. Highest Good-day share: 2020 (86.8%, 317 of 365 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 317 | 45 | 2 | 1 | 37 | 154 |
| 2021 | 294 | 55 | 7 | 1 | 37 | 154 |
| 2022 | 289 | 63 | 7 | 0 | 40 | 143 |
| 2023 | 261 | 74 | 19 | 2 | 41 | 154 |
| 2024 | 283 | 71 | 8 | 3 | 40 | 161 |
| 2025 | 272 | 64 | 20 | 3 | 40 | 156 |
How does Collin County compare?
How Collin 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 Collin 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.