DeForest, Wisconsin Air Quality
DeForest has a median AQI of 40, earning an air quality grade of A — excellent air quality that ranks better than 60% of US cities. Air quality has remained relatively stable over the past decade. Particulate matter (PM2.5) is the primary concern, often linked to vehicle traffic, industrial activity, and wildfire smoke. In 2025, DeForest recorded 130 good air quality days (72% of monitored days) and 1 unhealthy days.
Population: 11,501 • County: Dane
Current AQI
Quick Facts
| Current AQI | 17 — Good |
| Air Quality Grade | A |
| Median AQI (2025) | 40 |
| vs. U.S. Cities | Better than 60% |
| Primary Pollutant | PM2.5 |
| Unhealthy Days/Year | 1 |
| 10-Year Trend | → Stable |
| 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 DeForest is sourced from the Madison East monitoring area, located approximately 9 miles from city center. This EPA-certified station continuously tracks particulate matter (PM2.5), the primary driver of air quality alerts in this area.
DeForest tends to see elevated PM2.5 readings during fall and winter months when temperature inversions trap pollutants near the surface. Wood burning, vehicle exhaust, and reduced wind speeds compound the effect. Residents with respiratory conditions should monitor forecasts closely between November and February.
AQI Trend (10 Years)
Air Quality Days by Year
DeForest Median AQI by Year
Annual EPA air quality data for DeForest — median AQI, day-category breakdown, and primary pollutant per year.
| Year | Median AQI | Good Days | Unhealthy Days | Max AQI | Primary Pollutant |
|---|---|---|---|---|---|
| 2025 | 40 | 130 | 1 | 136 | PM2.5 |
| 2024 | 42 | 264 | — | 93 | PM2.5 |
| 2023 | 50 | 184 | 24 | 268 | PM2.5 |
| 2022 | 45 | 236 | — | 91 | PM2.5 |
| 2021 | 48 | 199 | 1 | 101 | PM2.5 |
| 2020 | 44 | 222 | 2 | 112 | PM2.5 |
| 2019 | 43 | 239 | — | 93 | PM2.5 |
| 2018 | 46 | 215 | 2 | 112 | PM2.5 |
| 2017 | 42 | 241 | — | 86 | PM2.5 |
| 2016 | 41 | 246 | — | 100 | PM2.5 |
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 DeForest Air Quality
What is the air quality in DeForest today?
The current AQI in DeForest is 17, 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 DeForest getting better or worse?
Air quality in DeForest has been stable. The median AQI has dropped 1 points (from 41 in 2016 to 40 in 2025).
What is the most common air pollutant in DeForest?
PM2.5 is the primary air pollutant in DeForest, responsible for 121 days (67% of monitored days) in 2025. Particulate matter originates from vehicle exhaust, wildfires, construction, and industrial activity.
How many unhealthy air days does DeForest have per year?
In 2025, DeForest recorded 72% good air quality days (130 days) out of 181 monitored days. There were 1 Unhealthy for Sensitive Groups days and 0 Unhealthy days (AQI above 100). The highest single-day AQI recorded was 136.
What air quality grade does DeForest receive?
DeForest receives an air quality grade of A, placing it better than 60% of US cities. This is based on a median AQI of 40 in 2025, with 130 good air quality days. The EPA monitors air quality in this area continuously using certified monitoring stations.
Air Quality Grade
Better than 60% of US cities
Nearby Cities
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National Rankings
See how DeForest compares to every other US city by air quality.
Best Air Quality Cities →All city rankingsRecommended Air Purifiers for DeForest
DeForest sees its worst PM2.5 during winter temperature inversions when particulates get trapped near ground level. A unit with True HEPA and an auto-mode sensor is most effective for responding to these spikes.
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