Median AQI
27
Good
Nebraska · County air quality · 2025
Washington County, Nebraska
Median AQI 27 (Good). 86.6% of monitored days rated Good, direct from EPA Air Quality System stations.
- 27
- Median AQI
- 86.6%
- Good-air days
- 0
- Unhealthy days
- 73%
- Cleaner than US counties
Washington County's 2025 annual median AQI is 27 (Good), with 86.6% Good days
According to the U.S. EPA Air Quality System, Washington County, Nebraska posted a 2025 median AQI of 27 (Good) across 336 monitored days, with 86.6% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Washington County's 86.6% Good-day share places it cleaner than 73% of US counties in 2025.
- Closest median-AQI peer
- Brown County (83.6% Good, median AQI 27) is the closest nationwide median-AQI peer to Washington County.
- 2020–2025 trend
- Washington County's floor-qualifying Good-day share is stable from 2020 to 2025 (84.5% → 86.6%).
- Median AQI
- Median AQI: 27
The verdict
According to EPA Air Quality System monitoring data, Washington County's air is good on balance, cleaner than the median US county, a median AQI of 27 with 86.6% of 336 monitored days in the Good band, driven mainly by PM2.5.
- 27
- median AQI · Good
- 86.6%
- days rated Good
- PM2.5
- main pollutant
- 73%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 132.
Annual release change
What changed in the 2025 EPA annual release
- Washington County's Good-day share rose from 75.7% to 86.6% between the 2024 and 2025 EPA annual releases, a change of +10.9 percentage points.
- Washington County's peak single-day AQI rose from 81 to 132 between the 2024 and 2025 EPA annual releases, a change of +51 points.
- Washington County's median AQI fell from 34 to 27 between the 2024 and 2025 EPA annual releases, a change of -7 points.
Data updated August 2026
- Good · 291 d · 86.6%
- Moderate · 44 d · 13.1%
- USG · 1 d · 0.3%
How did Washington County's air break down in 2025?
Across 336 monitored days, 291 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 132 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 336 days monitored. Median AQI: 27 (Good).
Insights: Washington County, Nebraska. EPA monitors recorded a median Air Quality Index of 27 across 336 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 291 (87%) fell in the Good band (AQI 0–50), 44 (13%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 53, while the worst single-day peak hit 132 (USG). Residents averaged about 26.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (336 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by +2.1 points (measured against 110 monitored days in 2020 and 336 in 2025, so raw day counts are not comparable) and the median AQI moved -4 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 132, usg but never Unhealthy. Nearby counties show comparable readings: Cass (95.9% good, AQI 19); Douglas (71.0% good, AQI 42); Gage (75.8% good, AQI 34); Hall (82.5% good, AQI 34); Knox (92.0% good, AQI 36); Lancaster (85.4% good, AQI 37).
Air Quality Summary
Good Days
86.6%
291 of 336 monitored days
11.6pp vs 75% target
Max AQI Recorded
132
USG
Health Grade
Good
90th-pct AQI 53
Washington County, Good days share 86.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
Washington 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 336 monitored days across EPA AQI categories.
Good
291
87%
Moderate
44
13%
USG
1
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 Washington County.
- PM2.5 · 336 days · 100.0%
Health Impact Assessment
Good
Washington County's air quality is rated Good based on 86.6% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 86.6% of monitored days in 2025, with a median AQI of 27. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 336 of 336 monitored days.
5-Year Air Quality Trend
Air quality is stable in Washington County. Highest Good-day share: 2022 (93.6%, 280 of 299 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 93 | 17 | 0 | 0 | 31 | 75 |
| 2021 | 83 | 25 | 1 | 0 | 37 | 125 |
| 2022 | 280 | 19 | 0 | 0 | 19 | 64 |
| 2023 | 258 | 98 | 3 | 1 | 33 | 154 |
| 2024 | 268 | 86 | 0 | 0 | 34 | 81 |
| 2025 | 291 | 44 | 1 | 0 | 27 | 132 |
How does Washington County compare?
How Washington County compares
Good-day share better than US avg
Washington County 86.6%
Brown County, South Dakota 83.6%
US average 76.0%
Median AQI better than US avg
Washington County 27
Brown County, South Dakota 27
US average 39
Unhealthy days / yr better than US avg
Washington County 0
Brown County, South Dakota 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Washington County (27), not geographic neighbors.
Brown County, South Dakota
Median AQI 27 · 83.6% Good-day share
Columbia County, Oregon
Median AQI 27 · 92.9% Good-day share
Linn County, Oregon
Median AQI 27 · 80.0% Good-day share
Oneida County, New York
Median AQI 27 · 84.4% Good-day share
Orange County, New York
Median AQI 27 · 86.9% Good-day share
Prowers County, Colorado
Median AQI 27 · 92.6% 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).
Franklin County, Washington
86.7% Good-day share · median AQI 23
Wyoming County, Pennsylvania
86.5% Good-day share · median AQI 24
Whitman County, Washington
86.8% Good-day share · median AQI 23
Wasco County, Oregon
86.3% Good-day share · median AQI 25
Perry County, Kentucky
87.1% Good-day share · median AQI 36
Hawaii County, Hawaii
86.0% Good-day share · median AQI 32
Nebraska counties on the map
Geographic containment only, other monitored counties in Nebraska, independent of AQI or pollutant match.
What Washington 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 27 means for exposure. Health guidance
- See how Washington County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Washington County with its Nebraska neighbours before drawing a conclusion about the region. All of Nebraska
Based on 336 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 Washington County, Nebraska? ▼
Washington County has a median Air Quality Index (AQI) of 27, rated "Good." 86.6% of monitored days (291 out of 336) had good air quality in 2025.
What is the main pollutant in Washington County? ▼
The primary pollutant in Washington County is Fine Particles (PM2.5), which was the main AQI driver on 336 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Washington County have? ▼
In 2025, Washington County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 132.
Is the air quality in Washington County getting better or worse? ▼
Air quality in Washington County is stable across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2022 at 93.6% (280 of 299 days). Lowest qualifying Good-day share: 2023 at 71.7% (258 of 360 days).
What does AQI 27 mean for health? ▼
Washington County's median AQI of 27 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Washington County compare to other counties in Nebraska? ▼
Washington County has 86.6% good air days. Nearby counties in Nebraska: Cass (95.9% good), Douglas (71.0% good), Gage (75.8% good), Hall (82.5% good), Knox (92.0% good), Lancaster (85.4% good).
What is the 90th percentile AQI in Washington County? ▼
The 90th percentile AQI for Washington County is 53, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 132 (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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Washington County, Nebraska · 2020–2025
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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.