EnviroNearby

Sioux County, Nebraska air quality history

Daily Air Quality Index summaries from EPA monitors in Sioux, Nebraska, 2007–2025.

87%
Good days in 2025
42
Median daily AQI, 2025
0
Days above 100 in 2025
214
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Sioux, Nebraska on 214 days. 187 of those days (87%) were in the Good range, and the median daily AQI was 42. That median is higher than the typical monitored county in Nebraska (median 34 across 10 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 214 days.

EPA did not report an AQI for every day of 2025 here (214 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.

Years with fewer than 120 monitored days (2007, 2009) 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%2007: Good 35 of 65 days2007: Moderate 30 of 65 days20072008: Good 66 of 128 days2008: Moderate 60 of 128 days2008: Unhealthy for Sensitive Groups 2 of 128 days20082009: Good 90 of 108 days2009: Moderate 18 of 108 days20092024: Good 254 of 319 days2024: Moderate 57 of 319 days2024: Unhealthy for Sensitive Groups 8 of 319 days20242025: Good 187 of 214 days2025: Moderate 27 of 214 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 year0501002007: 90th percentile AQI 802008: 90th percentile AQI 742009: 90th percentile AQI 542024: 90th percentile AQI 672025: 90th percentile AQI 582007: Median AQI 492008: Median AQI 502009: Median AQI 452024: Median AQI 442025: Median AQI 4220072008200920242025
  • 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
Ozone214100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20252141872700004258100Ozone
20243192545780004467143Ozone
200910890180000455474Ozone
2008128666020005074105Ozone
20076535300000498097Ozone

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 Nebraska with a similar median AQI in 2025

All monitored counties in Nebraska

Source: U.S. EPA AirData, “Annual AQI by County” files for 2007–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem