Kentucky · County air quality · 2025
Simpson County, Kentucky
Median AQI 39 (Good). 93.4% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 93.4%
- Good-air days
- 0
- Unhealthy days
- 88%
- Cleaner than US counties
Simpson County's 2025 annual median AQI is 39 (Good), with 93.4% Good days
According to the U.S. EPA Air Quality System, Simpson County, Kentucky posted a 2025 median AQI of 39 (Good) across 243 monitored days, with 93.4% 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
- Simpson County's 93.4% Good-day share places it cleaner than 88% of US counties in 2025.
- Closest median-AQI peer
- Aiken County (90.6% Good, median AQI 39) is the closest nationwide median-AQI peer to Simpson County.
- 2020–2025 trend
- Simpson County's floor-qualifying Good-day share is worsening from 2020 to 2025 (98.2% → 93.4%).
- Median AQI
- Median AQI: 39
According to the 2025 EPA AQS county release on PlainAirData, Simpson County, Kentucky ranks #392 of 951 by median AQI (39) and #114 by good-day share (93.4%). 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.
Annual release change
What changed in the 2025 EPA annual release
- Simpson County's Good-day share rose from 84.3% to 93.4% between the 2024 and 2025 EPA annual releases, a change of +9.1 percentage points.
- Simpson County's peak single-day AQI fell from 97 to 74 between the 2024 and 2025 EPA annual releases, a change of -23 points.
- Simpson County's median AQI fell from 43 to 39 between the 2024 and 2025 EPA annual releases, a change of -4 points.
Data updated August 2026
- Good · 227 d · 93.4%
- Moderate · 16 d · 6.6%
How did Simpson County's air break down in 2025?
Across 243 monitored days, 227 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 74 (Moderate).
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 Simpson County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Simpson County's Good-day share is 93.4% - cleaner than 88% of that comparison set.
Simpson County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
93.4% Cleaner than 88% higher than 88% 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 Simpson County.
- Ozone · 243 days · 100.0%
2024 daily-monitor rhythm in Simpson County
Month-by-month median AQI from EPA day-level county monitors (242 reported days in 2024). Jun posted the highest typical readings (median AQI 47, peak 93); Sep was cleanest at median 38.
Five-year seasonal record
EPA day-level county files · 2020–20241,191 daily readings show a recurring local pattern: Jun has the highest matched-month median AQI (47), while Oct is lowest (35). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Simpson County's air quality is rated Excellent based on 93.4% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 93.4% of monitored days in 2025, with a median AQI of 39. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 243 of 243 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Simpson County. Highest Good-day share: 2020 (98.2%, 217 of 221 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 217 | 4 | 0 | 0 | 36 | 67 |
| 2021 | 222 | 21 | 0 | 0 | 37 | 90 |
| 2022 | 217 | 24 | 0 | 0 | 39 | 93 |
| 2023 | 204 | 33 | 7 | 0 | 43 | 122 |
| 2024 | 204 | 38 | 0 | 0 | 43 | 97 |
| 2025 | 227 | 16 | 0 | 0 | 39 | 74 |
How does Simpson County compare?
How Simpson 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 Simpson County, Kentucky · 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.