Median AQI
44
Good
Idaho · County air quality · 2025
Butte County, Idaho
Median AQI 44 (Good). 87.4% of monitored days rated Good, direct from EPA Air Quality System stations.
- 44
- Median AQI
- 87.4%
- Good-air days
- 0
- Unhealthy days
- 70%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Butte County's air is good on balance, cleaner than the median US county, a median AQI of 44 with 87.4% of 222 monitored days in the Good band, driven mainly by Ozone.
- 44
- median AQI · Good
- 87.4%
- days rated Good
- Ozone
- main pollutant
- 70%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 77.
Data updated July 2026
- Good · 194 d · 87.4%
- Moderate · 28 d · 12.6%
How did Butte County's air break down in 2025?
Across 222 monitored days, 194 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 77 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 222 days monitored. Median AQI: 44 (Good).
Insights: Butte County, Idaho. EPA monitors recorded a median Air Quality Index of 44 across 222 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 194 (87%) fell in the Good band (AQI 0–50), 28 (13%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 54, while the worst single-day peak hit 77 (Moderate). Residents averaged about 26.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (222 days). Across the 2020–2025 trend window, good days shifted by -140 and the median AQI moved +4 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 77, moderate but never Unhealthy. Nearby counties show comparable readings: Ada (80.6% good, AQI 39); Bannock (91.5% good, AQI 31); Benewah (74.6% good, AQI 37); Blaine (99.4% good, AQI 22); Boise (72.9% good, AQI 43); Bonner (71.3% good, AQI 41).
Air Quality Summary
Good Days
87.4%
194 of 222 monitored days
12.4pp vs 75% target
Max AQI Recorded
77
Moderate
Health Grade
Good
90th-pct AQI 54
Butte County, Good days share 87.4%
National avg
Share of monitored days at AQI 0-50 (Good band).
Butte County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 222 monitored days across EPA AQI categories.
Good
194
87%
Moderate
28
13%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Butte County.
- Ozone · 222 days · 100.0%
Health Impact Assessment
Good
Butte County's air quality is rated Good based on 87.4% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 87.4% of monitored days in 2025, with a median AQI of 44. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 222 of 222 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Butte County. Best year: 2022 (337 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 334 | 28 | 1 | 1 | 40 | 152 |
| 2021 | 289 | 71 | 3 | 0 | 42 | 128 |
| 2022 | 337 | 28 | 0 | 0 | 42 | 79 |
| 2023 | 320 | 42 | 0 | 0 | 44 | 80 |
| 2024 | 303 | 54 | 0 | 0 | 42 | 97 |
| 2025 | 194 | 28 | 0 | 0 | 44 | 77 |
How does Butte County compare?
How Butte County compares
Good-day share better than US avg
Butte County 87.4%
Ada County, Idaho 80.6%
US average 76.5%
Median AQI worse than US avg
Butte County 44
Ada County, Idaho 39
US average 38
Unhealthy days / yr about average
Butte County 0
Ada County, Idaho 0
US average 0
Other Counties in Idaho
Air quality comparison for nearby counties in Idaho.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Butte County.
Baltimore County, Maryland
AQI 44 · 70.4% good
Baltimore (City) County, Maryland
AQI 44 · 68.7% good
Bartholomew County, Indiana
AQI 44 · 69.2% good
Berks County, Pennsylvania
AQI 44 · 65.6% good
Bolivar County, Mississippi
AQI 44 · 70.3% good
Brewster County, Texas
AQI 44 · 69.0% good
What Butte County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 44 means for exposure. Health guidance
- See how Butte County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Butte County with its Idaho neighbours before drawing a conclusion about the region. All of Idaho
Based on 222 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Butte County, Idaho? ▼
Butte County has a median Air Quality Index (AQI) of 44, rated "Good." 87.4% of monitored days (194 out of 222) had good air quality in 2025.
What is the main pollutant in Butte County? ▼
The primary pollutant in Butte County is Ozone (O3), which was the main AQI driver on 222 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Butte County have? ▼
In 2025, Butte County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 77.
Is the air quality in Butte County getting better or worse? ▼
Air quality in Butte County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 337 good days. Worst year: 2025 with 194 good days.
What does AQI 44 mean for health? ▼
Butte County's median AQI of 44 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Butte County compare to other counties in Idaho? ▼
Butte County has 87.4% good air days. Nearby counties in Idaho: Ada (80.6% good), Bannock (91.5% good), Benewah (74.6% good), Blaine (99.4% good), Boise (72.9% good), Bonner (71.3% good).
What is the 90th percentile AQI in Butte County? ▼
The 90th percentile AQI for Butte County is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 77 (Moderate).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.