Illinois · County air quality · 2025
Jo Daviess County, Illinois
Median AQI 33 (Good). 95.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 33
- Median AQI
- 95.3%
- Good-air days
- 0
- Unhealthy days
- 93%
- Cleaner than US counties
Jo Daviess County's 2025 annual median AQI is 33 (Good), with 95.3% Good days
According to the U.S. EPA Air Quality System, Jo Daviess County, Illinois posted a 2025 median AQI of 33 (Good) across 341 monitored days, with 95.3% 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
- Jo Daviess County's 95.3% Good-day share places it cleaner than 93% of US counties in 2025.
- Closest median-AQI peer
- Apache County (86.2% Good, median AQI 33) is the closest nationwide median-AQI peer to Jo Daviess County.
- 2020–2025 trend
- Jo Daviess County's floor-qualifying Good-day share is stable from 2020 to 2025 (95.5% → 95.3%).
- Median AQI
- Median AQI: 33
According to the 2025 EPA AQS county release on PlainAirData, Jo Daviess County, Illinois ranks #123 of 951 by median AQI (33) and #71 by good-day share (95.3%). 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
- Jo Daviess County's Good-day share rose from 93.7% to 95.3% between the 2024 and 2025 EPA annual releases, a change of +1.6 percentage points.
- Jo Daviess County's peak single-day AQI fell from 101 to 87 between the 2024 and 2025 EPA annual releases, a change of -14 points.
- Jo Daviess County's median AQI fell from 36 to 33 between the 2024 and 2025 EPA annual releases, a change of -3 points.
Data updated August 2026
- Good · 325 d · 95.3%
- Moderate · 16 d · 4.7%
How did Jo Daviess County's air break down in 2025?
Across 341 monitored days, 325 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 87 (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 Jo Daviess County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Jo Daviess County's Good-day share is 95.3% - cleaner than 93% of that comparison set.
Jo Daviess County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
95.3% Cleaner than 93% higher than 93% 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 Jo Daviess County.
- Ozone · 341 days · 100.0%
2024 daily-monitor rhythm in Jo Daviess County
Month-by-month median AQI from EPA day-level county monitors (349 reported days in 2024). May posted the highest typical readings (median AQI 46, peak 80); Dec was cleanest at median 22. Summer months (Jun–Aug) averaged median AQI 41 vs 27 in Dec–Feb.
Five-year seasonal record
EPA day-level county files · 2020–20241,760 daily readings show a recurring local pattern: Jun has the highest matched-month median AQI (52), while Dec is lowest (23). 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
Jo Daviess County's air quality is rated Excellent based on 95.3% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 95.3% of monitored days in 2025, with a median AQI of 33. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 341 of 341 monitored days.
5-Year Air Quality Trend
Air quality is stable in Jo Daviess County. Highest Good-day share: 2022 (95.6%, 328 of 343 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 337 | 16 | 0 | 0 | 32 | 87 |
| 2021 | 336 | 26 | 0 | 0 | 36 | 97 |
| 2022 | 328 | 15 | 0 | 0 | 34 | 84 |
| 2023 | 302 | 42 | 8 | 1 | 36 | 154 |
| 2024 | 327 | 21 | 1 | 0 | 36 | 101 |
| 2025 | 325 | 16 | 0 | 0 | 33 | 87 |
How does Jo Daviess County compare?
How Jo Daviess 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 Jo Daviess County, Illinois · 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.