EnviroNearby

Latah County, Idaho air quality history

Daily Air Quality Index summaries from EPA monitors in Latah, Idaho, 1987–2025.

83%
Good days in 2025
31
Median daily AQI, 2025
1
Days above 100 in 2025
338
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Latah, Idaho on 338 days. 282 of those days (83%) were in the Good range, and the median daily AQI was 31. 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 338 days. Across the years with fuller monitoring, the share of Good days fell: an average of 89% in 2004–2006 versus 84% in 2023–2025.

Years with fewer than 120 monitored days (1987, 1988, 2002, 2003, 2013) 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%1987: Good 32 of 46 days1987: Moderate 14 of 46 days19871988: Good 14 of 15 days1988: Moderate 1 of 15 days2002: Good 23 of 31 days2002: Moderate 8 of 31 days20022003: Good 25 of 25 days2004: Good 248 of 292 days2004: Moderate 44 of 292 days20042005: Good 336 of 353 days2005: Moderate 17 of 353 days2006: Good 298 of 342 days2006: Moderate 38 of 342 days2006: Unhealthy for Sensitive Groups 6 of 342 days20062007: Good 313 of 353 days2007: Moderate 40 of 353 days2008: Good 313 of 340 days2008: Moderate 27 of 340 days20082009: Good 307 of 322 days2009: Moderate 15 of 322 days2010: Good 261 of 277 days2010: Moderate 16 of 277 days20102011: Good 342 of 365 days2011: Moderate 23 of 365 days2012: Good 299 of 347 days2012: Moderate 42 of 347 days2012: Unhealthy for Sensitive Groups 2 of 347 days2012: Unhealthy 4 of 347 days20122013: Good 34 of 34 days2015: Good 231 of 265 days2015: Moderate 26 of 265 days2015: Unhealthy for Sensitive Groups 2 of 265 days2015: Unhealthy 4 of 265 days2015: Very Unhealthy 2 of 265 days20152016: Good 264 of 270 days2016: Moderate 6 of 270 days2017: Good 309 of 350 days2017: Moderate 30 of 350 days2017: Unhealthy for Sensitive Groups 5 of 350 days2017: Unhealthy 3 of 350 days2017: Very Unhealthy 3 of 350 days20172018: Good 327 of 365 days2018: Moderate 32 of 365 days2018: Unhealthy for Sensitive Groups 5 of 365 days2018: Unhealthy 1 of 365 days2019: Good 343 of 350 days2019: Moderate 7 of 350 days20192020: Good 319 of 361 days2020: Moderate 35 of 361 days2020: Unhealthy 1 of 361 days2020: Very Unhealthy 4 of 361 days2020: Hazardous 2 of 361 days2021: Good 309 of 360 days2021: Moderate 41 of 360 days2021: Unhealthy for Sensitive Groups 5 of 360 days2021: Unhealthy 5 of 360 days20212022: Good 312 of 361 days2022: Moderate 44 of 361 days2022: Unhealthy for Sensitive Groups 1 of 361 days2022: Unhealthy 4 of 361 days2023: Good 320 of 360 days2023: Moderate 38 of 360 days2023: Unhealthy for Sensitive Groups 1 of 360 days2023: Unhealthy 1 of 360 days20232024: Good 297 of 366 days2024: Moderate 68 of 366 days2024: Unhealthy for Sensitive Groups 1 of 366 days2025: Good 282 of 338 days2025: Moderate 55 of 338 days2025: Unhealthy for Sensitive Groups 1 of 338 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 year0501001987: 90th percentile AQI 681988: 90th percentile AQI 502002: 90th percentile AQI 552003: 90th percentile AQI 302004: 90th percentile AQI 532005: 90th percentile AQI 412006: 90th percentile AQI 532007: 90th percentile AQI 512008: 90th percentile AQI 462009: 90th percentile AQI 392010: 90th percentile AQI 392011: 90th percentile AQI 382012: 90th percentile AQI 562013: 90th percentile AQI 222015: 90th percentile AQI 562016: 90th percentile AQI 292017: 90th percentile AQI 542018: 90th percentile AQI 522019: 90th percentile AQI 352020: 90th percentile AQI 522021: 90th percentile AQI 572022: 90th percentile AQI 532023: 90th percentile AQI 522024: 90th percentile AQI 582025: 90th percentile AQI 571987: Median AQI 351988: Median AQI 212002: Median AQI 322003: Median AQI 222004: Median AQI 262005: Median AQI 202006: Median AQI 212007: Median AQI 192008: Median AQI 182009: Median AQI 182010: Median AQI 132011: Median AQI 142012: Median AQI 162013: Median AQI 132015: Median AQI 142016: Median AQI 102017: Median AQI 182018: Median AQI 142019: Median AQI 142020: Median AQI 212021: Median AQI 202022: Median AQI 132023: Median AQI 222024: Median AQI 272025: Median AQI 311987200220042006200820102012201520172019202120232025
  • 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)338100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253382825510003157107PM2.5
20243662976810002758117PM2.5
20233603203811002252183PM2.5
20223613124414001353192PM2.5
20213603094155002057195PM2.5
20203613193501422152415PM2.5
201935034370000143555PM2.5
20183653273251001452184PM2.5
20173503093053301854271PM2.5
201627026460000102963PM2.5
20152652312624201456231PM2.5
2013343400000132236PM2.5
20123472994224001656180PM2.5
2011365342230000143874PM2.5
2010277261160000133970PM2.5
2009322307150000183968PM2.5
2008340313270000184671PM2.5
2007353313400000195183PM2.5
20063422983860002153140PM2.5
2005353336170000204174PM2.5
2004292248440000265368PM2.5
2003252500000223046PM2.5
2002312380000325568PM2.5
1988151410000215053PM10
19874632140000356884PM10

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 1987–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem