EnviroNearby

Franklin County, Idaho air quality history

Daily Air Quality Index summaries from EPA monitors in Franklin, Idaho, 2004–2025.

96%
Good days in 2025
21
Median daily AQI, 2025
0
Days above 100 in 2025
351
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Franklin, Idaho on 351 days. 338 of those days (96%) were in the Good range, and the median daily AQI was 21. That median is lower than the typical monitored county in Idaho (median 35 across 18 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 351 days. Across the years with fuller monitoring, the share of Good days rose: an average of 80% in 2005–2007 versus 89% in 2023–2025.

Years with fewer than 120 monitored days (2004, 2008, 2009, 2010) 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%2004: Good 8 of 16 days2004: Moderate 8 of 16 days20042005: Good 235 of 314 days2005: Moderate 57 of 314 days2005: Unhealthy for Sensitive Groups 14 of 314 days2005: Unhealthy 8 of 314 days2006: Good 246 of 291 days2006: Moderate 44 of 291 days2006: Unhealthy for Sensitive Groups 1 of 291 days20062007: Good 172 of 211 days2007: Moderate 37 of 211 days2007: Unhealthy for Sensitive Groups 2 of 211 days2008: Good 79 of 90 days2008: Moderate 10 of 90 days2008: Unhealthy for Sensitive Groups 1 of 90 days20082009: Good 80 of 105 days2009: Moderate 21 of 105 days2009: Unhealthy for Sensitive Groups 4 of 105 days2010: Good 9 of 33 days2010: Moderate 21 of 33 days2010: Unhealthy for Sensitive Groups 2 of 33 days2010: Unhealthy 1 of 33 days20102011: Good 227 of 312 days2011: Moderate 76 of 312 days2011: Unhealthy for Sensitive Groups 4 of 312 days2011: Unhealthy 5 of 312 days2012: Good 244 of 366 days2012: Moderate 118 of 366 days2012: Unhealthy for Sensitive Groups 4 of 366 days20122013: Good 259 of 357 days2013: Moderate 66 of 357 days2013: Unhealthy for Sensitive Groups 21 of 357 days2013: Unhealthy 11 of 357 days2014: Good 318 of 359 days2014: Moderate 39 of 359 days2014: Unhealthy for Sensitive Groups 2 of 359 days20142015: Good 285 of 335 days2015: Moderate 45 of 335 days2015: Unhealthy for Sensitive Groups 4 of 335 days2015: Unhealthy 1 of 335 days2016: Good 271 of 357 days2016: Moderate 79 of 357 days2016: Unhealthy for Sensitive Groups 7 of 357 days20162017: Good 239 of 365 days2017: Moderate 112 of 365 days2017: Unhealthy for Sensitive Groups 9 of 365 days2017: Unhealthy 5 of 365 days2018: Good 249 of 319 days2018: Moderate 67 of 319 days2018: Unhealthy for Sensitive Groups 3 of 319 days20182019: Good 315 of 364 days2019: Moderate 46 of 364 days2019: Unhealthy for Sensitive Groups 3 of 364 days2020: Good 297 of 365 days2020: Moderate 65 of 365 days2020: Unhealthy for Sensitive Groups 2 of 365 days2020: Unhealthy 1 of 365 days20202021: Good 285 of 365 days2021: Moderate 74 of 365 days2021: Unhealthy for Sensitive Groups 6 of 365 days2022: Good 310 of 365 days2022: Moderate 54 of 365 days2022: Unhealthy for Sensitive Groups 1 of 365 days20222023: Good 310 of 361 days2023: Moderate 47 of 361 days2023: Unhealthy for Sensitive Groups 3 of 361 days2023: Unhealthy 1 of 361 days2024: Good 304 of 358 days2024: Moderate 54 of 358 days20242025: Good 338 of 351 days2025: Moderate 13 of 351 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 year0501002004: 90th percentile AQI 552005: 90th percentile AQI 792006: 90th percentile AQI 582007: 90th percentile AQI 572008: 90th percentile AQI 522009: 90th percentile AQI 782010: 90th percentile AQI 992011: 90th percentile AQI 692012: 90th percentile AQI 632013: 90th percentile AQI 932014: 90th percentile AQI 532015: 90th percentile AQI 572016: 90th percentile AQI 642017: 90th percentile AQI 692018: 90th percentile AQI 612019: 90th percentile AQI 542020: 90th percentile AQI 582021: 90th percentile AQI 662022: 90th percentile AQI 562023: 90th percentile AQI 542024: 90th percentile AQI 562025: 90th percentile AQI 392004: Median AQI 512005: Median AQI 312006: Median AQI 272007: Median AQI 272008: Median AQI 282009: Median AQI 262010: Median AQI 582011: Median AQI 382012: Median AQI 422013: Median AQI 302014: Median AQI 252015: Median AQI 282016: Median AQI 342017: Median AQI 372018: Median AQI 252019: Median AQI 232020: Median AQI 262021: Median AQI 282022: Median AQI 232023: Median AQI 242024: Median AQI 222025: Median AQI 21200420062008201020122014201620182020202220242025
  • 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)351100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025351338130000213982PM2.5
2024358304540000225688PM2.5
20233613104731002454155PM2.5
20223653105410002356103PM2.5
20213652857460002866119PM2.5
20203652976521002658162PM2.5
20193643154630002354112PM2.5
20183192496730002561124PM2.5
201736523911295003769172PM2.5
20163572717970003464125PM2.5
20153352854541002857170PM2.5
20143593183920002553105PM2.5
2013357259662111003093184PM2.5
201236624411840004263125PM2.5
20113122277645003869172PM2.5
20103392121005899161PM2.5
2009105802140002678134PM2.5
200890791010002852140PM2.5
20072111723720002757117PM2.5
20062912464410002758113PM2.5
200531423557148003179171PM2.5
200416880000515556PM2.5

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 Idaho with a similar median AQI in 2025

All monitored counties in Idaho

Source: U.S. EPA AirData, “Annual AQI by County” files for 2004–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem