EnviroNearby

Jefferson County, Oregon air quality history

Daily Air Quality Index summaries from EPA monitors in Jefferson, Oregon, 2008–2025.

74%
Good days in 2025
28
Median daily AQI, 2025
0
Days above 100 in 2025
361
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Jefferson, Oregon on 361 days. 267 of those days (74%) were in the Good range, and the median daily AQI was 28. That median is about the same as the typical monitored county in Oregon (median 29 across 21 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 361 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 73% in 2009–2011 versus 75% in 2023–2025.

Years with fewer than 120 monitored days (2008, 2014, 2015, 2017) 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%2008: Good 27 of 63 days2008: Moderate 36 of 63 days20082009: Good 251 of 365 days2009: Moderate 113 of 365 days2009: Unhealthy 1 of 365 days2010: Good 261 of 365 days2010: Moderate 103 of 365 days2010: Unhealthy 1 of 365 days20102011: Good 131 of 165 days2011: Moderate 34 of 165 days2012: Good 116 of 145 days2012: Moderate 29 of 145 days20122013: Good 212 of 265 days2013: Moderate 53 of 265 days2014: Good 52 of 82 days2014: Moderate 28 of 82 days2014: Unhealthy 2 of 82 days20142015: Good 60 of 92 days2015: Moderate 28 of 92 days2015: Unhealthy for Sensitive Groups 3 of 92 days2015: Unhealthy 1 of 92 days2017: Good 54 of 92 days2017: Moderate 29 of 92 days2017: Unhealthy for Sensitive Groups 5 of 92 days2017: Unhealthy 3 of 92 days2017: Very Unhealthy 1 of 92 days20172018: Good 96 of 184 days2018: Moderate 82 of 184 days2018: Unhealthy for Sensitive Groups 5 of 184 days2018: Unhealthy 1 of 184 days2019: Good 261 of 365 days2019: Moderate 102 of 365 days2019: Unhealthy for Sensitive Groups 2 of 365 days20192020: Good 258 of 361 days2020: Moderate 92 of 361 days2020: Unhealthy for Sensitive Groups 3 of 361 days2020: Very Unhealthy 3 of 361 days2020: Hazardous 5 of 361 days2021: Good 282 of 365 days2021: Moderate 77 of 365 days2021: Unhealthy for Sensitive Groups 4 of 365 days2021: Unhealthy 2 of 365 days20212022: Good 272 of 365 days2022: Moderate 92 of 365 days2022: Unhealthy for Sensitive Groups 1 of 365 days2023: Good 266 of 365 days2023: Moderate 93 of 365 days2023: Unhealthy for Sensitive Groups 3 of 365 days2023: Unhealthy 1 of 365 days2023: Very Unhealthy 2 of 365 days20232024: Good 289 of 366 days2024: Moderate 76 of 366 days2024: Unhealthy for Sensitive Groups 1 of 366 days2025: Good 267 of 361 days2025: Moderate 94 of 361 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 year0501002008: 90th percentile AQI 762009: 90th percentile AQI 672010: 90th percentile AQI 612011: 90th percentile AQI 682012: 90th percentile AQI 582013: 90th percentile AQI 542014: 90th percentile AQI 672015: 90th percentile AQI 812017: 90th percentile AQI 992018: 90th percentile AQI 722019: 90th percentile AQI 662020: 90th percentile AQI 642021: 90th percentile AQI 612022: 90th percentile AQI 632023: 90th percentile AQI 632024: 90th percentile AQI 592025: 90th percentile AQI 632008: Median AQI 542009: Median AQI 372010: Median AQI 332011: Median AQI 282012: Median AQI 322013: Median AQI 312014: Median AQI 442015: Median AQI 422017: Median AQI 372018: Median AQI 492019: Median AQI 292020: Median AQI 282021: Median AQI 282022: Median AQI 262023: Median AQI 312024: Median AQI 262025: Median AQI 28200820102012201420172019202120232025
  • 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
Fine particles (PM2.5)361100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025361267940000286390PM2.5
20243662897610002659142PM2.5
20233652669331203163238PM2.5
20223652729210002663108PM2.5
20213652827742002861173PM2.5
202036125892303528641135PM2.5
201936526110220002966122PM2.5
2018184968251004972156PM2.5
201792542953103799242PM2.5
201592602831004281160PM2.5
201482522802004467184PM2.5
2013265212530000315473PM2.5
2012145116290000325878PM2.5
2011165131340000286899PM2.5
201036526110301003361172PM2.5
200936525111301003767200PM2.5
20086327360000547695PM2.5

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 Oregon with a similar median AQI in 2025

All monitored counties in Oregon

Source: U.S. EPA AirData, “Annual AQI by County” files for 2008–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem