EnviroNearby

St Thomas, Virgin Islands air quality history

Daily Air Quality Index summaries from EPA monitors in St Thomas, Virgin Islands, 1995–2020.

73%
Good days in 2019
37
Median daily AQI, 2019
0
Days above 100 in 2019
268
Days with an AQI in 2019 (of 365)

In 2019, EPA reported a daily Air Quality Index (AQI) for St Thomas, Virgin Islands on 268 days. 195 of those days (73%) were in the Good range, and the median daily AQI was 37. That median is lower than the typical monitored U.S. county (41). The main pollutant was fine particles (PM2.5) on 268 days.

EPA did not report an AQI for every day of 2019 here (268 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

The most recent year with data for this county is 2020; EPA's files for 2021–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (2004, 2005, 2006, 2007, 2009, 2020…) 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%1995: Good 2 of 2 days19951996: Good 34 of 35 days1996: Moderate 1 of 35 days1997: Good 48 of 52 days1997: Moderate 4 of 52 days19971998: Good 44 of 44 days1999: Good 51 of 54 days1999: Moderate 3 of 54 days19992000: Good 39 of 54 days2000: Moderate 15 of 54 days2001: Good 40 of 54 days2001: Moderate 14 of 54 days20012002: Good 40 of 48 days2002: Moderate 8 of 48 days2003: Good 45 of 64 days2003: Moderate 15 of 64 days2003: Unhealthy for Sensitive Groups 4 of 64 days20032004: Good 43 of 49 days2004: Moderate 6 of 49 days2005: Good 35 of 41 days2005: Moderate 6 of 41 days20052006: Good 19 of 23 days2006: Moderate 4 of 23 days2007: Good 14 of 16 days2007: Moderate 2 of 16 days20072008: Good 119 of 142 days2008: Moderate 23 of 142 days2009: Good 103 of 112 days2009: Moderate 9 of 112 days20092018: Good 127 of 183 days2018: Moderate 55 of 183 days2018: Unhealthy for Sensitive Groups 1 of 183 days2019: Good 195 of 268 days2019: Moderate 73 of 268 days20192020: Good 58 of 75 days2020: Moderate 17 of 75 days2020
  • 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 year0501001995: 90th percentile AQI 471996: 90th percentile AQI 381997: 90th percentile AQI 351998: 90th percentile AQI 301999: 90th percentile AQI 472000: 90th percentile AQI 642001: 90th percentile AQI 562002: 90th percentile AQI 552003: 90th percentile AQI 772004: 90th percentile AQI 542005: 90th percentile AQI 552006: 90th percentile AQI 572007: 90th percentile AQI 532008: 90th percentile AQI 542009: 90th percentile AQI 452018: 90th percentile AQI 602019: 90th percentile AQI 622020: 90th percentile AQI 611995: Median AQI 471996: Median AQI 171997: Median AQI 191998: Median AQI 161999: Median AQI 162000: Median AQI 342001: Median AQI 312002: Median AQI 242003: Median AQI 332004: Median AQI 282005: Median AQI 222006: Median AQI 312007: Median AQI 302008: Median AQI 272009: Median AQI 252018: Median AQI 362019: Median AQI 372020: Median AQI 311995199719992001200320052007200920192020
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2019

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
Fine particles (PM2.5)268100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20207558170000316175PM2.5
2019268195730000376292PM2.5
20181831275510003660126PM2.5
200911210390000254583PM10
2008142119230000275492PM10
2007161420000305355PM10
2006231940000315770PM2.5
2005413560000225562PM10
2004494360000285477PM2.5
200364451540003377110PM2.5
2002484080000245568PM10
20015440140000315694PM2.5
20005439150000346483PM10
1999545130000164779PM10
1998444400000163044PM10
1997524840000193582PM10
1996353410000173881PM10
19952200000474747PM10

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.

All monitored counties in Virgin Islands

Source: U.S. EPA AirData, “Annual AQI by County” files for 1995–2020 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem