Median AQI
39
Good
Louisiana · County air quality · 2025
Terrebonne County, Louisiana
Median AQI 39 (Good). 77.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 77.0%
- Good-air days
- 0
- Unhealthy days
- 44%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Terrebonne County's air is good on balance, more polluted than the median US county, a median AQI of 39 with 77.0% of 61 monitored days in the Good band, driven mainly by PM2.5.
- 39
- median AQI · Good
- 77.0%
- days rated Good
- PM2.5
- main pollutant
- 44%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 66.
Data updated July 2026
- Good · 47 d · 77.0%
- Moderate · 14 d · 23.0%
How did Terrebonne County's air break down in 2025?
Across 61 monitored days, 47 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 66 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 61 days monitored. Median AQI: 39 (Good).
Insights: Terrebonne County, Louisiana. EPA monitors recorded a median Air Quality Index of 39 across 61 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 47 (77%) fell in the Good band (AQI 0–50), 14 (23%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 57, while the worst single-day peak hit 66 (Moderate). Residents averaged about 23.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (61 days). Across the 2020–2025 trend window, good days shifted by -45 and the median AQI moved +3 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 66, moderate but never Unhealthy. Nearby counties show comparable readings: Ascension (94.1% good, AQI 33); Bossier (86.5% good, AQI 40); Caddo (84.3% good, AQI 38); Calcasieu (61.5% good, AQI 47); East Baton Rouge (49.3% good, AQI 51); Iberville (78.4% good, AQI 41).
Air Quality Summary
Good Days
77.0%
47 of 61 monitored days
2.0pp vs 75% target
Max AQI Recorded
66
Moderate
Health Grade
Good
90th-pct AQI 57
Terrebonne County, Good days share 77.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Terrebonne 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 61 monitored days across EPA AQI categories.
Good
47
77%
Moderate
14
23%
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 Terrebonne County.
- PM2.5 · 61 days · 100.0%
Health Impact Assessment
Good
Terrebonne County's air quality is rated Good based on 77.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 77.0% of monitored days in 2025, with a median AQI of 39. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 61 of 61 monitored days.
5-Year Air Quality Trend
Air quality is stable in Terrebonne County. Best year: 2020 (92 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 92 | 28 | 0 | 0 | 36 | 77 |
| 2021 | 89 | 21 | 0 | 0 | 34 | 64 |
| 2022 | 90 | 31 | 0 | 0 | 38 | 96 |
| 2023 | 77 | 35 | 2 | 1 | 43 | 176 |
| 2024 | 85 | 38 | 0 | 0 | 39 | 99 |
| 2025 | 47 | 14 | 0 | 0 | 39 | 66 |
How does Terrebonne County compare?
How Terrebonne County compares
Good-day share better than US avg
Terrebonne County 77.0%
Ascension County, Louisiana 94.1%
US average 76.5%
Median AQI worse than US avg
Terrebonne County 39
Ascension County, Louisiana 33
US average 38
Unhealthy days / yr about average
Terrebonne County 0
Ascension County, Louisiana 0
US average 0
Other Counties in Louisiana
Air quality comparison for nearby counties in Louisiana.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Terrebonne County.
Ada County, Idaho
AQI 39 · 80.6% good
Aiken County, South Carolina
AQI 39 · 89.1% good
Albany County, New York
AQI 39 · 67.4% good
Alexander County, North Carolina
AQI 39 · 92.4% good
Ashland County, Wisconsin
AQI 39 · 85.6% good
Bennington County, Vermont
AQI 39 · 82.9% good
What Terrebonne 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 39 means for exposure. Health guidance
- See how Terrebonne County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Terrebonne County with its Louisiana neighbours before drawing a conclusion about the region. All of Louisiana
Based on 61 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 Terrebonne County, Louisiana? ▼
Terrebonne County has a median Air Quality Index (AQI) of 39, rated "Good." 77.0% of monitored days (47 out of 61) had good air quality in 2025.
What is the main pollutant in Terrebonne County? ▼
The primary pollutant in Terrebonne County is Fine Particles (PM2.5), which was the main AQI driver on 61 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Terrebonne County have? ▼
In 2025, Terrebonne County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 66.
Is the air quality in Terrebonne County getting better or worse? ▼
Air quality in Terrebonne County is stable based on 5-year trends (2020-2025). Best year: 2020 with 92 good days. Worst year: 2025 with 47 good days.
What does AQI 39 mean for health? ▼
Terrebonne County's median AQI of 39 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 Terrebonne County compare to other counties in Louisiana? ▼
Terrebonne County has 77.0% good air days. Nearby counties in Louisiana: Ascension (94.1% good), Bossier (86.5% good), Caddo (84.3% good), Calcasieu (61.5% good), East Baton Rouge (49.3% good), Iberville (78.4% good).
What is the 90th percentile AQI in Terrebonne County? ▼
The 90th percentile AQI for Terrebonne County is 57, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 66 (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.