Median AQI
20
Good
Nebraska · County air quality · 2025
Cass County, Nebraska
Median AQI 20 (Good). 96.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 20
- Median AQI
- 96.5%
- Good-air days
- 0
- Unhealthy days
- 93%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Cass County's air is good on balance, among the cleanest 10% of US counties, a median AQI of 20 with 96.5% of 288 monitored days in the Good band, driven mainly by PM10.
- 20
- median AQI · Good
- 96.5%
- days rated Good
- PM10
- main pollutant
- 93%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 64.
Data updated July 2026
- Good · 278 d · 96.5%
- Moderate · 10 d · 3.5%
How did Cass County's air break down in 2025?
Across 288 monitored days, 278 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 64 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 288 days monitored. Median AQI: 20 (Good).
Insights: Cass County, Nebraska. EPA monitors recorded a median Air Quality Index of 20 across 288 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 278 (97%) fell in the Good band (AQI 0–50), 10 (3%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 35, while the worst single-day peak hit 64 (Moderate). Residents averaged about 29.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM10 (288 days). Across the 2020–2025 trend window, good days shifted by -68 and the median AQI moved +6 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 64, moderate but never Unhealthy. Nearby counties show comparable readings: Douglas (66.8% good, AQI 44); Gage (74.0% good, AQI 36); Hall (80.2% good, AQI 37); Knox (89.3% good, AQI 39); Lancaster (77.7% good, AQI 36); Sarpy (77.1% good, AQI 33).
Air Quality Summary
Good Days
96.5%
278 of 288 monitored days
21.5pp vs 75% target
Max AQI Recorded
64
Moderate
Health Grade
Excellent
90th-pct AQI 35
Cass County, Good days share 96.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Cass 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 288 monitored days across EPA AQI categories.
Good
278
97%
Moderate
10
3%
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 Cass County.
- PM10 · 288 days · 100.0%
Health Impact Assessment
Excellent
Cass County's air quality is rated Excellent based on 96.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 96.5% of monitored days in 2025, with a median AQI of 20. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM10, driving AQI on 288 of 288 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Cass County. Best year: 2020 (346 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 346 | 12 | 0 | 0 | 14 | 71 |
| 2021 | 345 | 6 | 0 | 0 | 19 | 64 |
| 2022 | 337 | 19 | 0 | 0 | 19 | 87 |
| 2023 | 344 | 10 | 0 | 0 | 17 | 66 |
| 2024 | 259 | 15 | 0 | 0 | 17 | 68 |
| 2025 | 278 | 10 | 0 | 0 | 20 | 64 |
How does Cass County compare?
How Cass County compares
Good-day share better than US avg
Cass County 96.5%
Douglas County, Nebraska 66.8%
US average 76.5%
Median AQI better than US avg
Cass County 20
Douglas County, Nebraska 44
US average 38
Unhealthy days / yr about average
Cass County 0
Douglas County, Nebraska 0
US average 0
Other Counties in Nebraska
Air quality comparison for nearby counties in Nebraska.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Cass County.
Hyde County, North Carolina
AQI 20 · 100.0% good
Whitman County, Washington
AQI 20 · 93.8% good
Adams County, Washington
AQI 19 · 94.7% good
Bonneville County, Idaho
AQI 19 · 94.9% good
Cowlitz County, Washington
AQI 21 · 91.6% good
Elko County, Nevada
AQI 19 · 90.8% good
What Cass County's air means for you
The air here stays in the breathable range year-round, with PM10 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM10 days, the guide explains what a median of 20 means for exposure. Health guidance
- See how Cass County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Cass County with its Nebraska neighbours before drawing a conclusion about the region. All of Nebraska
Based on 288 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 Cass County, Nebraska? ▼
Cass County has a median Air Quality Index (AQI) of 20, rated "Good." 96.5% of monitored days (278 out of 288) had good air quality in 2025.
What is the main pollutant in Cass County? ▼
The primary pollutant in Cass County is Coarse Particles (PM10), which was the main AQI driver on 288 days (100% of monitored days). Irritates airways and can aggravate asthma and bronchitis.
How many unhealthy air days does Cass County have? ▼
In 2025, Cass County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 64.
Is the air quality in Cass County getting better or worse? ▼
Air quality in Cass County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 346 good days. Worst year: 2024 with 259 good days.
What does AQI 20 mean for health? ▼
Cass County's median AQI of 20 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 Cass County compare to other counties in Nebraska? ▼
Cass County has 96.5% good air days. Nearby counties in Nebraska: Douglas (66.8% good), Gage (74.0% good), Hall (80.2% good), Knox (89.3% good), Lancaster (77.7% good), Sarpy (77.1% good).
What is the 90th percentile AQI in Cass County? ▼
The 90th percentile AQI for Cass County is 35, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 64 (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.