Iowa · County air quality · 2025
Webster County, Iowa
Median AQI 45 (Good). 59.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 45
- Median AQI
- 59.2%
- Good-air days
- 2
- Unhealthy days
- 14%
- Cleaner than US counties
Webster County's 2025 annual median AQI is 45 (Good), with 59.2% Good days
According to the U.S. EPA Air Quality System, Webster County, Iowa posted a 2025 median AQI of 45 (Good) across 184 monitored days, with 59.2% rated Good and 2 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Webster County's 59.2% Good-day share places it cleaner than 14% of US counties in 2025.
- Closest median-AQI peer
- Baltimore County (64.7% Good, median AQI 45) is the closest nationwide median-AQI peer to Webster County.
- Median AQI
- Median AQI: 45
- Good days
- Good days: 59.2%
According to the 2025 EPA AQS county release on PlainAirData, Webster County, Iowa ranks #750 of 951 by median AQI (45) and #817 by good-day share (59.2%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.
Data updated August 2026
- Good · 109 d · 59.2%
- Moderate · 71 d · 38.6%
- USG · 2 d · 1.1%
- Unhealthy · 2 d · 1.1%
How did Webster County's air break down in 2025?
Across 184 monitored days, 109 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 →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Webster County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Webster County's Good-day share is 59.2% - cleaner than 14% of that comparison set.
Webster County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
59.2% 14th percentile higher than 14% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Webster County.
- PM2.5 · 158 days · 85.9%
- PM10 · 26 days · 14.1%
Health Impact Assessment
Webster County's air quality is rated Moderate based on 59.2% 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 158 of 184 monitored days.
How does Webster County compare?
How Webster County compares
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 Webster County, Iowa · 2020–2025
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.