EnviroNearby

Knox County, Nebraska air quality history

Daily Air Quality Index summaries from EPA monitors in Knox, Nebraska, 2006–2025.

92%
Good days in 2025
36
Median daily AQI, 2025
4
Days above 100 in 2025
348
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Knox, Nebraska on 348 days. 320 of those days (92%) were in the Good range, and the median daily AQI was 36. That median is about the same as the typical monitored county in Nebraska (median 34 across 10 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 348 days. Across the years with fuller monitoring, the share of Good days fell: an average of 91% in 2006–2009 versus 88% in 2023–2025.

Years with fewer than 120 monitored days (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%2006: Good 133 of 160 days2006: Moderate 25 of 160 days2006: Very Unhealthy 2 of 160 days20062007: Good 85 of 85 days2008: Good 321 of 337 days2008: Moderate 16 of 337 days20082009: Good 345 of 360 days2009: Moderate 15 of 360 days2010: Good 324 of 349 days2010: Moderate 25 of 349 days20102011: Good 299 of 329 days2011: Moderate 29 of 329 days2011: Unhealthy for Sensitive Groups 1 of 329 days2012: Good 262 of 352 days2012: Moderate 77 of 352 days2012: Unhealthy for Sensitive Groups 13 of 352 days20122013: Good 339 of 364 days2013: Moderate 25 of 364 days2014: Good 318 of 342 days2014: Moderate 24 of 342 days20142015: Good 322 of 348 days2015: Moderate 26 of 348 days2016: Good 323 of 350 days2016: Moderate 26 of 350 days2016: Unhealthy for Sensitive Groups 1 of 350 days20162017: Good 304 of 338 days2017: Moderate 34 of 338 days2018: Good 329 of 357 days2018: Moderate 28 of 357 days20182019: Good 342 of 355 days2019: Moderate 13 of 355 days2020: Good 341 of 365 days2020: Moderate 24 of 365 days20202021: Good 317 of 358 days2021: Moderate 36 of 358 days2021: Unhealthy for Sensitive Groups 5 of 358 days2022: Good 319 of 355 days2022: Moderate 36 of 355 days20222023: Good 271 of 341 days2023: Moderate 56 of 341 days2023: Unhealthy for Sensitive Groups 13 of 341 days2023: Unhealthy 1 of 341 days2024: Good 300 of 327 days2024: Moderate 26 of 327 days2024: Unhealthy for Sensitive Groups 1 of 327 days20242025: Good 320 of 348 days2025: Moderate 24 of 348 days2025: Unhealthy for Sensitive Groups 4 of 348 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 year0501002006: 90th percentile AQI 542007: 90th percentile AQI 382008: 90th percentile AQI 482009: 90th percentile AQI 462010: 90th percentile AQI 492011: 90th percentile AQI 502012: 90th percentile AQI 802013: 90th percentile AQI 492014: 90th percentile AQI 482015: 90th percentile AQI 482016: 90th percentile AQI 482017: 90th percentile AQI 512018: 90th percentile AQI 482019: 90th percentile AQI 462020: 90th percentile AQI 482021: 90th percentile AQI 542022: 90th percentile AQI 512023: 90th percentile AQI 802024: 90th percentile AQI 492025: 90th percentile AQI 482006: Median AQI 322007: Median AQI 312008: Median AQI 342009: Median AQI 332010: Median AQI 362011: Median AQI 372012: Median AQI 382013: Median AQI 362014: Median AQI 352015: Median AQI 362016: Median AQI 352017: Median AQI 362018: Median AQI 342019: Median AQI 352020: Median AQI 352021: Median AQI 372022: Median AQI 372023: Median AQI 412024: Median AQI 362025: Median AQI 3620062008201020122014201620182020202220242025
  • 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
Ozone348100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253483202440003648115Ozone
20243273002610003649108Ozone
202334127156131004180151Ozone
20223553193600003751100Ozone
20213583173650003754112Ozone
2020365341240000354884Ozone
2019355342130000354680Ozone
2018357329280000344893Ozone
20173383043400003651100Ozone
20163503232610003548101Ozone
2015348322260000364887Ozone
2014342318240000354880Ozone
20133643392500003649100Ozone
201235226277130003880133Ozone
20113292992910003750101Ozone
2010349324250000364990Ozone
2009360345150000334680Ozone
2008337321160000344874Ozone
2007858500000313842Ozone
20061601332500203254202Ozone

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 2006–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem