EnviroNearby

Caribou County, Idaho air quality history

Daily Air Quality Index summaries from EPA monitors in Caribou, Idaho, 1986–2004.

88%
Good days in 1989
24
Median daily AQI, 1989
0
Days above 100 in 1989
219
Days with an AQI in 1989 (of 365)

In 1989, EPA reported a daily Air Quality Index (AQI) for Caribou, Idaho on 219 days. 193 of those days (88%) were in the Good range, and the median daily AQI was 24. That median is lower than the typical monitored county in Idaho (median 33 across 4 counties), and lower than the typical monitored U.S. county (39). The main pollutant was coarse particles (PM10) on 219 days.

EPA did not report an AQI for every day of 1989 here (219 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.

The most recent year with data for this county is 2004; EPA's files for 2005–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (1999, 2000, 2001, 2002, 2003, 2004…) 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%1986: Good 43 of 54 days1986: Moderate 10 of 54 days1986: Unhealthy for Sensitive Groups 1 of 54 days19861987: Good 46 of 54 days1987: Moderate 8 of 54 days1988: Good 87 of 119 days1988: Moderate 30 of 119 days1988: Unhealthy for Sensitive Groups 2 of 119 days19881989: Good 193 of 219 days1989: Moderate 26 of 219 days1990: Good 90 of 97 days1990: Moderate 7 of 97 days19901991: Good 45 of 48 days1991: Moderate 3 of 48 days1992: Good 39 of 43 days1992: Moderate 4 of 43 days19921993: Good 58 of 59 days1993: Moderate 1 of 59 days1994: Good 57 of 61 days1994: Moderate 4 of 61 days19941995: Good 59 of 61 days1995: Moderate 2 of 61 days1996: Good 59 of 61 days1996: Moderate 2 of 61 days19961997: Good 53 of 55 days1997: Moderate 2 of 55 days1998: Good 49 of 58 days1998: Moderate 9 of 58 days19981999: Good 53 of 56 days1999: Moderate 3 of 56 days2000: Good 32 of 33 days2000: Moderate 1 of 33 days20002001: Good 57 of 57 days2002: Good 46 of 47 days2002: Moderate 1 of 47 days20022003: Good 48 of 51 days2003: Moderate 3 of 51 days2004: Good 12 of 16 days2004: Moderate 4 of 16 days2004
  • 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 year0501001986: 90th percentile AQI 631987: 90th percentile AQI 671988: 90th percentile AQI 631989: 90th percentile AQI 531990: 90th percentile AQI 471991: 90th percentile AQI 441992: 90th percentile AQI 491993: 90th percentile AQI 411994: 90th percentile AQI 401995: 90th percentile AQI 321996: 90th percentile AQI 411997: 90th percentile AQI 291998: 90th percentile AQI 541999: 90th percentile AQI 402000: 90th percentile AQI 352001: 90th percentile AQI 342002: 90th percentile AQI 342003: 90th percentile AQI 402004: 90th percentile AQI 571986: Median AQI 211987: Median AQI 171988: Median AQI 241989: Median AQI 241990: Median AQI 191991: Median AQI 201992: Median AQI 231993: Median AQI 201994: Median AQI 221995: Median AQI 161996: Median AQI 171997: Median AQI 181998: Median AQI 171999: Median AQI 182000: Median AQI 132001: Median AQI 172002: Median AQI 162003: Median AQI 242004: Median AQI 271986198819901992199419961998200020022004
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 1989

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
Coarse particles (PM10)219100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2004161240000275762PM2.5
2003514830000244069PM2.5
2002474610000163463PM10
2001575700000173447PM10
2000333210000133555PM10
1999565330000184068PM10
1998584990000175477PM10
1997555320000182955PM10
1996615920000174162PM10
1995615920000163260PM10
1994615740000224063PM10
1993595810000204151PM10
19924339400002349100PM10
1991484530000204453PM10
1990979070000194778PM10
1989219193260000245389PM10
1988119873020002463120PM10
1987544680000176785PM10
198654431010002163109PM10

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.

All monitored counties in Idaho

Source: U.S. EPA AirData, “Annual AQI by County” files for 1986–2004 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem