Median AQI
19
Good
Idaho · County air quality · 2025
Bonneville County, Idaho
Median AQI 19 (Good). 94.9% of monitored days rated Good, direct from EPA Air Quality System stations.
- 19
- Median AQI
- 94.9%
- Good-air days
- 0
- Unhealthy days
- 89%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Bonneville County's air is good on balance, cleaner than most US counties, a median AQI of 19 with 94.9% of 175 monitored days in the Good band, driven mainly by PM2.5.
- 19
- median AQI · Good
- 94.9%
- days rated Good
- PM2.5
- main pollutant
- 89%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 68.
Data updated July 2026
- Good · 166 d · 94.9%
- Moderate · 9 d · 5.1%
How did Bonneville County's air break down in 2025?
Across 175 monitored days, 166 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 68 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 175 days monitored. Median AQI: 19 (Good).
Insights: Bonneville County, Idaho. EPA monitors recorded a median Air Quality Index of 19 across 175 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 166 (95%) fell in the Good band (AQI 0–50), 9 (5%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 38, while the worst single-day peak hit 68 (Moderate). Residents averaged about 28.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (175 days). Across the 2020–2025 trend window, good days shifted by -132 and the median AQI moved -9 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 68, 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
94.9%
166 of 175 monitored days
19.9pp vs 75% target
Max AQI Recorded
68
Moderate
Health Grade
Excellent
90th-pct AQI 38
Bonneville County, Good days share 94.9%
National avg
Share of monitored days at AQI 0-50 (Good band).
Bonneville 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 175 monitored days across EPA AQI categories.
Good
166
95%
Moderate
9
5%
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 Bonneville County.
- PM2.5 · 175 days · 100.0%
Health Impact Assessment
Excellent
Bonneville County's air quality is rated Excellent based on 94.9% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 94.9% of monitored days in 2025, with a median AQI of 19. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 175 of 175 monitored days.
5-Year Air Quality Trend
Air quality is improving in Bonneville County. Best year: 2023 (326 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 298 | 59 | 1 | 4 | 28 | 155 |
| 2021 | 275 | 72 | 9 | 0 | 31 | 144 |
| 2022 | 306 | 50 | 1 | 0 | 27 | 109 |
| 2023 | 326 | 22 | 0 | 0 | 25 | 84 |
| 2024 | 316 | 48 | 0 | 0 | 22 | 91 |
| 2025 | 166 | 9 | 0 | 0 | 19 | 68 |
How does Bonneville County compare?
How Bonneville County compares
Good-day share better than US avg
Bonneville County 94.9%
Ada County, Idaho 80.6%
US average 76.5%
Median AQI better than US avg
Bonneville County 19
Ada County, Idaho 39
US average 38
Unhealthy days / yr about average
Bonneville 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 Bonneville County.
Adams County, Washington
AQI 19 · 94.7% good
Elko County, Nevada
AQI 19 · 90.8% good
Grays Harbor County, Washington
AQI 19 · 97.9% good
Jefferson County, Washington
AQI 19 · 96.5% good
Luna County, New Mexico
AQI 19 · 79.5% good
Mohave County, Arizona
AQI 19 · 93.4% good
What Bonneville County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 19 means for exposure. Health guidance
- See how Bonneville County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Bonneville County with its Idaho neighbours before drawing a conclusion about the region. All of Idaho
Based on 175 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 Bonneville County, Idaho? ▼
Bonneville County has a median Air Quality Index (AQI) of 19, rated "Good." 94.9% of monitored days (166 out of 175) had good air quality in 2025.
What is the main pollutant in Bonneville County? ▼
The primary pollutant in Bonneville County is Fine Particles (PM2.5), which was the main AQI driver on 175 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Bonneville County have? ▼
In 2025, Bonneville County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 68.
Is the air quality in Bonneville County getting better or worse? ▼
Air quality in Bonneville County is improving based on 5-year trends (2020-2025). Best year: 2023 with 326 good days. Worst year: 2025 with 166 good days.
What does AQI 19 mean for health? ▼
Bonneville County's median AQI of 19 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 Bonneville County compare to other counties in Idaho? ▼
Bonneville County has 94.9% 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 Bonneville County? ▼
The 90th percentile AQI for Bonneville County is 38, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 68 (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.