Median AQI
48
Good
Iowa · County air quality · 2025
Webster County, Iowa
Median AQI 48 (Good). 54.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 48
- Median AQI
- 54.5%
- Good-air days
- 2
- Unhealthy days
- 10%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Webster County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 48 with 54.5% of 123 monitored days in the Good band, driven mainly by PM2.5.
- 48
- median AQI · Good
- 54.5%
- days rated Good
- PM2.5
- main pollutant
- 10%
- cleaner than US counties
2 days reached Unhealthy or worse; the worst single reading hit AQI 165.
Data updated July 2026
- Good · 67 d · 54.5%
- Moderate · 52 d · 42.3%
- USG · 2 d · 1.6%
- Unhealthy · 2 d · 1.6%
How did Webster County's air break down in 2025?
Across 123 monitored days, 67 fell in the Good band (AQI 0–50) and 2 reached Unhealthy or worse. The worst single day peaked at AQI 165 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 123 days monitored. Median AQI: 48 (Good).
Insights: Webster County, Iowa. EPA monitors recorded a median Air Quality Index of 48 across 123 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 67 (54%) fell in the Good band (AQI 0–50), 52 (42%) registered Moderate readings, and 2 (2%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 68, while the worst single-day peak hit 165 (Unhealthy). Residents averaged about 16.3 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (104 days), PM10 (19 days). Across the 2025–2025 trend window, good days shifted by +0 and the median AQI moved +0 points, placing the multi-year trajectory at tracked. Residents and visitors experienced 2 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Black Hawk (56.6% good, AQI 48); Bremer (87.1% good, AQI 38); Clinton (59.9% good, AQI 45); Harrison (83.0% good, AQI 39); Johnson (71.0% good, AQI 36); Linn (61.2% good, AQI 44).
Air Quality Summary
Good Days
54.5%
67 of 123 monitored days
-20.5pp vs 75% target
Max AQI Recorded
165
Unhealthy
Health Grade
Moderate
90th-pct AQI 68
Webster County, Good days share 54.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Webster County, Unhealthy-or-worse share 1.6%
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 123 monitored days across EPA AQI categories.
Good
67
54%
Moderate
52
42%
USG
2
2%
Unhealthy
2
2%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Webster County.
- PM2.5 · 104 days · 84.6%
- PM10 · 19 days · 15.4%
Health Impact Assessment
Moderate
Webster County's air quality is rated Moderate based on 54.5% good air days. There were 2 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 2 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 165. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 104 of 123 monitored days.
How does Webster County compare?
How Webster County compares
Good-day share worse than US avg
Webster County 54.5%
Black Hawk County, Iowa 56.6%
US average 76.5%
Median AQI worse than US avg
Webster County 48
Black Hawk County, Iowa 48
US average 38
Unhealthy days / yr worse than US avg
Webster County 2
Black Hawk County, Iowa 1
US average 0
Other Counties in Iowa
Air quality comparison for nearby counties in Iowa.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Webster County.
Black Hawk County, Iowa
AQI 48 · 56.6% good
Box Elder County, Utah
AQI 48 · 60.0% good
Brookings County, South Dakota
AQI 48 · 53.0% good
Clear Creek County, Colorado
AQI 48 · 64.4% good
Coconino County, Arizona
AQI 48 · 62.5% good
Columbia County, Florida
AQI 48 · 56.4% good
What Webster County's air means for you
On most days the air here is fine, but PM2.5 drives 2 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 48 means for exposure. Health guidance
- See how Webster County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Webster County with its Iowa neighbours before drawing a conclusion about the region. All of Iowa
Based on 123 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 Webster County, Iowa? ▼
Webster County has a median Air Quality Index (AQI) of 48, rated "Good." 54.5% of monitored days (67 out of 123) had good air quality in 2025.
What is the main pollutant in Webster County? ▼
The primary pollutant in Webster County is Fine Particles (PM2.5), which was the main AQI driver on 104 days (85% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Webster County have? ▼
In 2025, Webster County recorded 2 unhealthy air days (2 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 165.
Is the air quality in Webster County getting better or worse? ▼
Insufficient trend data is available for Webster County.
What does AQI 48 mean for health? ▼
Webster County's median AQI of 48 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 Webster County compare to other counties in Iowa? ▼
Webster County has 54.5% good air days. Nearby counties in Iowa: Black Hawk (56.6% good), Bremer (87.1% good), Clinton (59.9% good), Harrison (83.0% good), Johnson (71.0% good), Linn (61.2% good).
What is the 90th percentile AQI in Webster County? ▼
The 90th percentile AQI for Webster County is 68, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 165 (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.
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.