Median AQI
40
Good
Idaho · County air quality · 2025
Idaho County, Idaho
Median AQI 40 (Good). 71.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 40
- Median AQI
- 71.8%
- Good-air days
- 6
- Unhealthy days
- 36%
- Cleaner than US counties
Idaho County's 2025 annual median AQI is 40 (Good), with 71.8% Good days
According to the U.S. EPA Air Quality System, Idaho County, Idaho posted a 2025 median AQI of 40 (Good) across 365 monitored days, with 71.8% rated Good and 6 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Idaho County's 71.8% Good-day share places it cleaner than 36% of US counties in 2025.
- Closest median-AQI peer
- Anderson County (91.3% Good, median AQI 40) is the closest nationwide median-AQI peer to Idaho County.
- 2020–2025 trend
- Idaho County's floor-qualifying Good-day share is improving from 2020 to 2025 (66.8% → 72.0%).
- Median AQI
- Median AQI: 40
The verdict
According to EPA Air Quality System monitoring data, Idaho County's air is good on balance, more polluted than the median US county, a median AQI of 40 with 71.8% of 365 monitored days in the Good band, driven mainly by PM2.5.
- 40
- median AQI · Good
- 71.8%
- days rated Good
- PM2.5
- main pollutant
- 36%
- cleaner than US counties
6 days reached Unhealthy or worse; the worst single reading hit AQI 215.
Annual release change
What changed in the 2025 EPA annual release
- Idaho County's Good-day share rose from 64.8% to 71.8% between the 2024 and 2025 EPA annual releases, a change of +7.0 percentage points.
- Idaho County's Unhealthy-category days rose from 2 to 5 between the 2024 and 2025 EPA annual releases, a change of +3 days.
Data updated August 2026
- Good · 262 d · 71.8%
- Moderate · 95 d · 26.0%
- USG · 2 d · 0.5%
- Unhealthy · 5 d · 1.4%
- Very Unhealthy · 1 d · 0.3%
How did Idaho County's air break down in 2025?
Across 365 monitored days, 262 fell in the Good band (AQI 0–50) and 6 reached Unhealthy or worse. The worst single day peaked at AQI 215 (Very Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 365 days monitored. Median AQI: 40 (Good).
Insights: Idaho County, Idaho. EPA monitors recorded a median Air Quality Index of 40 across 365 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 262 (72%) fell in the Good band (AQI 0–50), 95 (26%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 62, while the worst single-day peak hit 215 (Very Unhealthy). Residents averaged about 21.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (187 days), Ozone (178 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by +5.1 points and the median AQI moved +0 points, placing the multi-year trajectory at improving. The annual record contains 6 days at Unhealthy or worse. On those days, the EPA recommends that sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Ada (74.0% good, AQI 42); Bannock (88.8% good, AQI 36); Benewah (63.4% good, AQI 41); Blaine (96.6% good, AQI 17); Boise (70.4% good, AQI 42); Bonner (56.2% good, AQI 47).
Air Quality Summary
Good Days
71.8%
262 of 365 monitored days
-3.2pp vs 75% target
Max AQI Recorded
215
Very Unhealthy
Health Grade
Moderate
90th-pct AQI 62
Idaho County, Good days share 71.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Idaho County, Unhealthy-or-worse share 16.4%
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 365 monitored days across EPA AQI categories.
Good
262
72%
Moderate
95
26%
USG
2
1%
Unhealthy
5
1%
Very Unhealthy
1
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Idaho County.
- PM2.5 · 187 days · 51.2%
- Ozone · 178 days · 48.8%
Health Impact Assessment
Moderate
Idaho County's air quality is rated Moderate based on 71.8% good air days. There were 6 unhealthy days in 2025 when outdoor activity should be limited.
Air quality reached unhealthy levels on 6 days in 2025 (5 Unhealthy, 1 Very Unhealthy). Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, and adults over 65, should review the daily breakdown below and follow local air-quality advisories on high-AQI days.
Sensitive group advisory
People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.
The dominant pollutant is PM2.5, driving AQI on 187 of 365 monitored days.
5-Year Air Quality Trend
Air quality is improving in Idaho County. Highest Good-day share: 2025 (72.0%, 262 of 365 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 244 | 113 | 3 | 5 | 40 | 209 |
| 2021 | 237 | 112 | 9 | 7 | 42 | 188 |
| 2022 | 242 | 113 | 4 | 4 | 41 | 263 |
| 2023 | 233 | 132 | 0 | 0 | 44 | 98 |
| 2024 | 237 | 121 | 5 | 2 | 42 | 217 |
| 2025 | 262 | 95 | 2 | 5 | 40 | 215 |
How does Idaho County compare?
How Idaho County compares
Good-day share worse than typical
Idaho County 71.8%
Anderson County, South Carolina 91.3%
Typical US county 76.0%
Median AQI worse than typical
Idaho County 40
Anderson County, South Carolina 40
Typical US county 39
Unhealthy days / yr worse than typical
Idaho County 6
Anderson County, South Carolina 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Idaho County (40), not geographic neighbors.
Anderson County, South Carolina
Median AQI 40 · 91.3% Good-day share
Andrew County, Missouri
Median AQI 40 · 86.9% Good-day share
Anne Arundel County, Maryland
Median AQI 40 · 87.6% Good-day share
Bergen County, New Jersey
Median AQI 40 · 71.1% Good-day share
Blair County, Pennsylvania
Median AQI 40 · 76.9% Good-day share
Brazos County, Texas
Median AQI 40 · 68.5% Good-day share
Same primary pollutant: PM2.5
PM2.5 led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Durham County, North Carolina
71.8% Good-day share · median AQI 42
Bolivar County, Mississippi
71.9% Good-day share · median AQI 43
Sequoyah County, Oklahoma
71.9% Good-day share · median AQI 42
Mobile County, Alabama
71.6% Good-day share · median AQI 43
Collier County, Florida
72.0% Good-day share · median AQI 43
Cumberland County, Pennsylvania
71.5% Good-day share · median AQI 35
Idaho counties on the map
Geographic containment only, other monitored counties in Idaho, independent of AQI or pollutant match.
What Idaho County's air means for you
On most days the air here is fine, but PM2.5 drives 6 unhealthy-or-worse days a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 40 means for exposure. Health guidance
- See how Idaho County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Idaho County with its Idaho neighbours before drawing a conclusion about the region. All of Idaho
Based on 365 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Idaho County, Idaho? ▼
Idaho County has a median Air Quality Index (AQI) of 40, rated "Good." 71.8% of monitored days (262 out of 365) had good air quality in 2025.
What is the main pollutant in Idaho County? ▼
The primary pollutant in Idaho County is Fine Particles (PM2.5), which was the main AQI driver on 187 days (51% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Idaho County have? ▼
In 2025, Idaho County recorded 6 unhealthy air days (5 Unhealthy, 1 Very Unhealthy, 0 Hazardous). The maximum AQI reached 215.
Is the air quality in Idaho County getting better or worse? ▼
Air quality in Idaho County is improving across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2025 at 72.0% (262 of 365 days). Lowest qualifying Good-day share: 2023 at 63.8% (233 of 365 days).
What does AQI 40 mean for health? ▼
Idaho County's median AQI of 40 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Idaho County compare to other counties in Idaho? ▼
Idaho County has 71.8% good air days. Nearby counties in Idaho: Ada (74.0% good), Bannock (88.8% good), Benewah (63.4% good), Blaine (96.6% good), Boise (70.4% good), Bonner (56.2% good).
What is the 90th percentile AQI in Idaho County? ▼
The 90th percentile AQI for Idaho County is 62, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 215 (Very Unhealthy).
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Idaho County, Idaho · 2020–2025
Share this annual record
Send the source-year summary or download its ready-to-use data card.
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData 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.