EnviroNearby

St. Tammany Parish, Louisiana air quality history

Daily Air Quality Index summaries from EPA monitors in St. Tammany, Louisiana, 2005–2025.

87%
Good days in 2025
37
Median daily AQI, 2025
1
Days above 100 in 2025
363
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for St. Tammany, Louisiana on 363 days. 315 of those days (87%) were in the Good range, and the median daily AQI was 37. That median is lower than the typical monitored county in Louisiana (median 42 across 21 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 363 days. Across the years with fuller monitoring, the share of Good days rose: an average of 52% in 2008–2010 versus 78% in 2023–2025.

Years with fewer than 120 monitored days (2005, 2006, 2007) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%2005: Good 7 of 39 days2005: Moderate 32 of 39 days20052006: Good 10 of 56 days2006: Moderate 46 of 56 days2007: Good 3 of 11 days2007: Moderate 8 of 11 days20072008: Good 111 of 238 days2008: Moderate 118 of 238 days2008: Unhealthy for Sensitive Groups 9 of 238 days2009: Good 218 of 365 days2009: Moderate 143 of 365 days2009: Unhealthy for Sensitive Groups 3 of 365 days2009: Unhealthy 1 of 365 days20092010: Good 183 of 362 days2010: Moderate 174 of 362 days2010: Unhealthy for Sensitive Groups 3 of 362 days2010: Unhealthy 2 of 362 days2011: Good 216 of 365 days2011: Moderate 134 of 365 days2011: Unhealthy for Sensitive Groups 15 of 365 days20112012: Good 217 of 359 days2012: Moderate 139 of 359 days2012: Unhealthy for Sensitive Groups 3 of 359 days2013: Good 213 of 365 days2013: Moderate 148 of 365 days2013: Unhealthy for Sensitive Groups 3 of 365 days2013: Unhealthy 1 of 365 days20132014: Good 229 of 365 days2014: Moderate 127 of 365 days2014: Unhealthy for Sensitive Groups 9 of 365 days2015: Good 249 of 365 days2015: Moderate 116 of 365 days20152016: Good 271 of 363 days2016: Moderate 91 of 363 days2016: Unhealthy for Sensitive Groups 1 of 363 days2017: Good 271 of 364 days2017: Moderate 92 of 364 days2017: Unhealthy for Sensitive Groups 1 of 364 days20172018: Good 280 of 365 days2018: Moderate 84 of 365 days2018: Unhealthy for Sensitive Groups 1 of 365 days2019: Good 266 of 363 days2019: Moderate 97 of 363 days20192020: Good 268 of 364 days2020: Moderate 96 of 364 days2021: Good 288 of 352 days2021: Moderate 64 of 352 days20212022: Good 277 of 365 days2022: Moderate 87 of 365 days2022: Unhealthy for Sensitive Groups 1 of 365 days2023: Good 248 of 365 days2023: Moderate 116 of 365 days2023: Unhealthy for Sensitive Groups 1 of 365 days20232024: Good 291 of 362 days2024: Moderate 70 of 362 days2024: Unhealthy 1 of 362 days2025: Good 315 of 363 days2025: Moderate 47 of 363 days2025: Unhealthy for Sensitive Groups 1 of 363 days2025
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501002005: 90th percentile AQI 822006: 90th percentile AQI 842007: 90th percentile AQI 662008: 90th percentile AQI 802009: 90th percentile AQI 642010: 90th percentile AQI 742011: 90th percentile AQI 742012: 90th percentile AQI 662013: 90th percentile AQI 632014: 90th percentile AQI 672015: 90th percentile AQI 602016: 90th percentile AQI 562017: 90th percentile AQI 582018: 90th percentile AQI 612019: 90th percentile AQI 602020: 90th percentile AQI 572021: 90th percentile AQI 542022: 90th percentile AQI 592023: 90th percentile AQI 612024: 90th percentile AQI 572025: 90th percentile AQI 582005: Median AQI 592006: Median AQI 582007: Median AQI 542008: Median AQI 522009: Median AQI 462010: Median AQI 502011: Median AQI 462012: Median AQI 462013: Median AQI 462014: Median AQI 452015: Median AQI 432016: Median AQI 412017: Median AQI 412018: Median AQI 382019: Median AQI 412020: Median AQI 392021: Median AQI 372022: Median AQI 412023: Median AQI 422024: Median AQI 392025: Median AQI 3720052007200920112013201520172019202120232025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Ozone363100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253633154710003758105Ozone
20243622917001003957186Ozone
202336524811610004261105Ozone
20223652778710004159103PM2.5
2021352288640000375471PM2.5
2020364268960000395790PM2.5
2019363266970000416084Ozone
20183652808410003861101Ozone
20173642719210004158129Ozone
20163632719110004156119Ozone
201536524911600004360100PM2.5
201436522912790004567143PM2.5
201336521314831004663154PM2.5
201235921713930004666122PM2.5
2011365216134150004674143PM2.5
201036218317432005074159PM2.5
200936521814331004664159PM2.5
200823811111890005280150PM2.5
200711380000546666PM2.5
20065610460000588495PM2.5
2005397320000598292PM2.5

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Louisiana with a similar median AQI in 2025

All monitored counties in Louisiana

Source: U.S. EPA AirData, “Annual AQI by County” files for 2005–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem