Marengo, Wisconsin Air Quality
Marengo has a median AQI of 39, earning an air quality grade of A — excellent air quality that ranks better than 65% of US cities. Air quality has been trending worse over the past decade, a concern for local residents and health officials. Ground-level ozone is the primary concern, typically peaking on warm sunny days due to vehicle and industrial emissions. In 2025, Marengo recorded 155 good air quality days (86% of monitored days) and 3 unhealthy days.
Population: 149 • County: Ashland
Current AQI
Quick Facts
| Current AQI | 15 — Good |
| Air Quality Grade | A |
| Median AQI (2025) | 39 |
| vs. U.S. Cities | Better than 65% |
| Primary Pollutant | Ozone |
| Unhealthy Days/Year | 3 |
| 10-Year Trend | ↓ Worsening |
| Data Source | EPA AQS (historical) · AirNow (live) |
Health Recommendation
Air quality is satisfactory, and air pollution poses little or no risk.
It's a great day to be active outside!
5-Day AQI Forecast
Last 90 Days
Current Pollutant Levels
Real-time data from EPA AirNow
Local Air Quality Context
Air quality data for Marengo is sourced from the Bad River Tribal School monitoring area, located approximately 14 miles from city center. This EPA-certified station continuously tracks ground-level ozone, the primary driver of air quality alerts in this area.
Marengo typically sees its worst air quality during summer afternoons when heat and sunlight drive ground-level ozone formation from vehicle and industrial emissions. Morning readings are generally 15–25 points lower than afternoon peaks. Outdoor activity is best planned for early morning on high-ozone days.
AQI Trend (10 Years)
Air Quality Days by Year
Marengo Median AQI by Year
Annual EPA air quality data for Marengo — median AQI, day-category breakdown, and primary pollutant per year.
| Year | Median AQI | Good Days | Unhealthy Days | Max AQI | Primary Pollutant |
|---|---|---|---|---|---|
| 2025 | 39 | 155 | 3 | 188 | Ozone |
| 2024 | 34 | 331 | 1 | 101 | Ozone |
| 2023 | 40 | 272 | 6 | 115 | Ozone |
| 2022 | 36 | 334 | — | 74 | Ozone |
| 2021 | 37 | 282 | 4 | 160 | Ozone |
| 2020 | 34 | 336 | — | 72 | Ozone |
| 2019 | 35 | 332 | — | 81 | Ozone |
| 2018 | 36 | 324 | — | 84 | Ozone |
| 2017 | 33 | 357 | — | 87 | Ozone |
| 2016 | 32 | 342 | — | 80 | Ozone |
Source: EPA Air Quality System (AQS) annual summaries. "Unhealthy Days" includes Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous categories.
2025 Air Quality Summary
Primary Pollutant Days (2025)
Days when each pollutant was the primary driver of AQI. Learn about pollutants →
Frequently Asked Questions About Marengo Air Quality
What is the air quality in Marengo today?
The current AQI in Marengo is 15, rated "Good". Air quality is good — outdoor activity is safe for everyone today. Air quality is satisfactory, and air pollution poses little or no risk.
Is air quality in Marengo getting better or worse?
Air quality in Marengo has been worsening. The median AQI has risen 7 points (from 32 in 2016 to 39 in 2025), a concern for local health officials.
What is the most common air pollutant in Marengo?
Ozone is the primary air pollutant in Marengo, responsible for 138 days (76% of monitored days) in 2025. Ground-level ozone forms when sunlight reacts with emissions from vehicles and industry, typically peaking on hot summer afternoons.
How many unhealthy air days does Marengo have per year?
In 2025, Marengo recorded 86% good air quality days (155 days) out of 181 monitored days. There were 2 Unhealthy for Sensitive Groups days and 1 Unhealthy days (AQI above 100). The highest single-day AQI recorded was 188.
What air quality grade does Marengo receive?
Marengo receives an air quality grade of A, placing it better than 65% of US cities. This is based on a median AQI of 39 in 2025, with 155 good air quality days. The EPA monitors air quality in this area continuously using certified monitoring stations.
Air Quality Grade
Better than 65% of US cities
Nearby Cities
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National Rankings
See how Marengo compares to every other US city by air quality.
Best Air Quality Cities →All city rankingsRecommended Air Purifiers for Marengo
Marengo has a summer ozone problem — hot afternoons push AQI into Moderate or higher as sunlight converts vehicle and industrial emissions into ground-level ozone. Activated carbon and PECO filters chemically neutralize ozone rather than just trapping particles.
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