Median AQI
24
Good
Idaho · County air quality · 2025
Twin Falls County, Idaho
Median AQI 24 (Good). 97.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 24
- Median AQI
- 97.2%
- Good-air days
- 0
- Unhealthy days
- 94%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Twin Falls County's air is good on balance, among the cleanest 10% of US counties, a median AQI of 24 with 97.2% of 181 monitored days in the Good band, driven mainly by PM2.5.
- 24
- median AQI · Good
- 97.2%
- days rated Good
- PM2.5
- main pollutant
- 94%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 105.
Data updated July 2026
- Good · 176 d · 97.2%
- Moderate · 4 d · 2.2%
- USG · 1 d · 0.6%
How did Twin Falls County's air break down in 2025?
Across 181 monitored days, 176 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 105 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 181 days monitored. Median AQI: 24 (Good).
Insights: Twin Falls County, Idaho. EPA monitors recorded a median Air Quality Index of 24 across 181 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 176 (97%) fell in the Good band (AQI 0–50), 4 (2%) registered Moderate readings, and 1 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 38, while the worst single-day peak hit 105 (USG). Residents averaged about 29.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (181 days). Across the 2020–2025 trend window, good days shifted by -137 and the median AQI moved +0 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 105, usg 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
97.2%
176 of 181 monitored days
22.2pp vs 75% target
Max AQI Recorded
105
USG
Health Grade
Excellent
90th-pct AQI 38
Twin Falls County, Good days share 97.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Twin Falls 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 181 monitored days across EPA AQI categories.
Good
176
97%
Moderate
4
2%
USG
1
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Twin Falls County.
- PM2.5 · 181 days · 100.0%
Health Impact Assessment
Excellent
Twin Falls County's air quality is rated Excellent based on 97.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 97.2% of monitored days in 2025, with a median AQI of 24. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 181 of 181 monitored days.
5-Year Air Quality Trend
Air quality is improving in Twin Falls County. Best year: 2023 (328 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 313 | 44 | 3 | 4 | 24 | 163 |
| 2021 | 298 | 56 | 7 | 0 | 28 | 144 |
| 2022 | 280 | 71 | 1 | 1 | 31 | 155 |
| 2023 | 328 | 16 | 0 | 0 | 25 | 80 |
| 2024 | 264 | 76 | 4 | 3 | 23 | 158 |
| 2025 | 176 | 4 | 1 | 0 | 24 | 105 |
How does Twin Falls County compare?
How Twin Falls County compares
Good-day share better than US avg
Twin Falls County 97.2%
Ada County, Idaho 80.6%
US average 76.5%
Median AQI better than US avg
Twin Falls County 24
Ada County, Idaho 39
US average 38
Unhealthy days / yr about average
Twin Falls 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 Twin Falls County.
Alamosa County, Colorado
AQI 24 · 90.8% good
Anchorage County, Alaska
AQI 24 · 80.8% good
Charlton County, Georgia
AQI 24 · 79.0% good
Crook County, Oregon
AQI 24 · 80.7% good
Culberson County, Texas
AQI 24 · 80.0% good
Kootenai County, Idaho
AQI 24 · 88.4% good
What Twin Falls 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 24 means for exposure. Health guidance
- See how Twin Falls County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Twin Falls County with its Idaho neighbours before drawing a conclusion about the region. All of Idaho
Based on 181 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 Twin Falls County, Idaho? ▼
Twin Falls County has a median Air Quality Index (AQI) of 24, rated "Good." 97.2% of monitored days (176 out of 181) had good air quality in 2025.
What is the main pollutant in Twin Falls County? ▼
The primary pollutant in Twin Falls County is Fine Particles (PM2.5), which was the main AQI driver on 181 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Twin Falls County have? ▼
In 2025, Twin Falls County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 105.
Is the air quality in Twin Falls County getting better or worse? ▼
Air quality in Twin Falls County is improving based on 5-year trends (2020-2025). Best year: 2023 with 328 good days. Worst year: 2025 with 176 good days.
What does AQI 24 mean for health? ▼
Twin Falls County's median AQI of 24 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 Twin Falls County compare to other counties in Idaho? ▼
Twin Falls County has 97.2% 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 Twin Falls County? ▼
The 90th percentile AQI for Twin Falls County is 38, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 105 (USG).
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.