Wisconsinites breathed record-breaking levels of air pollution Thursday as wildfire smoke from northern Minnesota and Canada wafted across much of the Great Lakes region and the Northeast. Many monitoring stations across the state recorded pollution considered hazardous for the first time in at least 16 years — the span covered by most monitoring stations’ records.
As of 8 a.m. on Friday, Air Quality Index, or AQI, levels in Madison had peaked above 450 — far above the AQI’s 301 threshold for “hazardous” air quality, where everyone — not just sensitive groups — should take precautions to avoid breathing dangerous air.
Milwaukee’s AQI reached 644 earlier on Thursday — more than twice the hazardous threshold. Air quality deteriorated even further in northwestern Wisconsin, with the index reaching 967 along the Minnesota border earlier in the day.
Many Wisconsin communities, including Milwaukee, Waukesha, Odanah and Appleton, were still observing AQI over the 301 threshold Friday morning.
The index categories typically run only from zero to 500.
Thursday’s pollution surpassed levels once considered unprecedented. Before Canadian wildfire smoke pushed the AQI to record highs across Wisconsin in July 2023, cities including Madison, Milwaukee and Waukesha had not recorded an AQI above 200 since at least 2010, according to a Wisconsin Watch analysis of historical AQI data.
But wildfire smoke has elevated air pollution in Wisconsin each summer since 2023. Major cities have periodically recorded higher AQI readings around July, though Thursday’s levels were the first to surpass those recorded in 2023.
“This is a hazardous air quality episode that we have not experienced before,” Craig Czarnecki, air management outreach coordinator for the Wisconsin Department of Natural Resources, said in an email.
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Wildfires in northern Minnesota and Canada have caused some of the worst air quality on record for Wisconsin. The entire state remains under an Air Quality Advisory for fine particulate matter from wildfire smoke until noon on Friday, according to the Wisconsin Department of Natural Resources.
As of 2 p.m. Thursday, most of the state’s air quality was in the “very unhealthy” or “hazardous” Air Quality category. That means that everyone, not just sensitive groups, should avoid outdoor activities, the DNR said.
In areas near Superior, the Air Quality Index rose above 800, while parts of eastern Wisconsin including Milwaukee and Kenosha measured above 650. National Weather Service meteorologist Benjamin Sheppard told Wisconsin Watch these levels are some of the worst on record.
“What we’ve heard from some of our partners is that the Air Quality Index values that we’re seeing are definitely either never before seen or up there,” Sheppard said. “I’ve been working here for three years, and I’ve seen nothing anywhere near that high.”
Smoke from wildfires in northern Minnesota and Canada wafted in much of Wisconsin on July 16, 2026, including near the Capitol building in Madison. (Natalie Yahr / Wisconsin Watch)
Index values in Wisconsin have exceeded the records set by wildfires in June 2023, DNR spokesperson Craig Czarnecki said in an email, noting that the figures “will still need to be quality assured.” At that time, levels peaked at 273, which means concentrations in Superior and the Milwaukee area have more than doubled.
A Wisconsin Department of Natural Resources air quality map.
The U.S. Centers for Disease Control and Prevention recommends setting up a portable air cleaner or filter in a room that can be closed off from outside air and setting your air conditioner to recirculate mode if possible or close the outdoor intake damper.
Fine particulate matter, also known as PM2.5, is a main pollutant released from wildfire smoke that can enter the bloodstream. Dr. Joan Schiller, a member of Healthy Climate Wisconsin and retired medical oncologist, told WPR this can exacerbate lung conditions.
“I don’t think people realize how far away you can be from the fire itself and still have health problems,” Schiller said. “These health problems typically manifest themselves as respiratory problems, such as exacerbation of COPD or asthma or emphysema.”
How can I check the air quality in my area?
The Environmental Protection Agency monitors the air around the country and compiles an air quality index, or AQI.
(Courtesy of U.S. Environmental Protection Agency)
Here’s what to know about the index and how to keep tabs on your area, especially in U.S. regions dealing with smoke from Canadian wildfires.
What does the air quality index measure?
The index rates how clean or polluted the air is each day. The EPA uses this measure to keep tabs on five kinds of air pollutants. The main concern from the wildfire smoke is fine particle pollution. These particles are tiny enough to get deep into the lungs. They can cause short-term problems like coughing and itchy eyes and, in the long run, can affect the lungs and heart.
What do the numbers and colors mean?
The index categories typically only run from zero to 500 – although levels have reached well above 500 in multiple parts of the state. The higher the number, the worse the air quality. That range is broken down into six color-coded categories. Green or yellow — in the zero to 100 range — the air is pretty clear. Once it gets up to orange, the air quality could be a concern for sensitive groups like children, older adults or those with health conditions.
In the red and purple zones, the air quality is considered unhealthy for everyone.
And if the index gets to maroon — at 301 or above — pollution levels are hazardous.
At these high levels, take precautions to avoid breathing in the dangerous air. That can mean reducing your outdoor activities, running air purifiers inside and wearing a well-fitting mask like an N95 when you’re outside.
What’s the air quality right now?
Check AirNow.gov, which updates every hour. The site shows a real-time map of the air quality across the country and also includes a forecast for the day ahead. The map pulls in measurements from a network of air monitoring stations across the country. States and cities may also offer more local guidance.
Washington Park in Milwaukee is draped in smoke from wildfires in Canada and Minnesota on Thursday, July 16, 2026. (Jonathan Aguilar / Milwaukee Neighborhood News Service / CatchLight Local)
How long will smoke last in Wisconsin?
According to Sheppard and the National Weather Service (NWS), a southerly wind on Friday means smoke is anticipated to retreat from west to east – likely bringing an end to the advisory for much of the state.
“With those southwest winds, the air is going to get kind of clearer and healthier in a southwest to northeast manner,” Sheppard said. “Areas further north and east in Wisconsin are going to be most likely to hang on to that smoke.”
Areas along Lake Superior may also need to have the advisory extended, NWS said. But Sheppard said winds could bring back a second wave of smoke to the rest of the state as soon as Saturday.
“The weather models tentatively are telling us that the second batch of smoke could be as strong, or perhaps even worse,” he said.
The Associated Press contributed reporting, as did Hongyu Liu of Wisconsin Watch.
Wisconsin Watch is a nonprofit, nonpartisan newsroom. Subscribe to our newsletters for original stories and our Friday news roundup.
Smoky skies from Canada wildfires engulfed the Minneapolis skyline in 2015. (Photo by Getty Images)
The Minnesota Pollution Control Agency has issued an air quality alert for parts of Minnesota, including the Twin Cities metro area, for Tuesday through Friday, as wildfires in the northern parts of the state and Canada continue.
Hot temperatures and poor air quality can aggravate pre-existing health conditions and pose risks to people with asthma, heart disease, high blood pressure and diabetes, as well as pregnant women and children.
At extreme levels, smoke inhalation can lead to asthma attacks, heart attacks and strokes, so MPCA is advising at-risk Minnesotans to stay indoors. If you have symptoms, call your healthcare provider or 911 in an emergency.
The MPCA advises against “vigorous” outdoor activities, like sports, which could exacerbate any serious health or lung effects.
The Boundary Waters Canoe Area Wilderness in northern Minnesota indefinitely closed on Tuesday as more than 20 wildfires have broken out as a result of lightning strikes and dry air caused by the ongoing heat wave. Evacuations are currently underway in the Boundary Waters. At least 17 people have been rescued with no reported injuries.
Source: Minnesota Pollution Control Agency.
Smoke from the Superior National Forest is expected to head south over the next 24 hours.
Look for hazy skies as smoke moves across northeastern Minnesota to the southern and western parts of the state.
Even for those without preexisting health conditions, hazardous air quality can lead to shortness of breath, irritated eyes and nose, coughing and chest tightening.
Smoky air is expected in Brainerd, Alexandria, Hinckley, St. Cloud, Winona, Moorhead, International Falls, Two Harbors, Hibbing, Ely, Duluth, and the Tribal Nations of Mille Lacs, Prairie Island, Leech Lake, White Earth, Red Lake, Grand Portage and Fond du Lac.
Hazardous levels of smoke are expected in Two Harbors and Grant Portage; the MPCA advises residents there to avoid any outdoor activities and stay indoors.
For Minnesotans, climate change-induced smoky skies and poor air quality are becoming a near annual summer event; the state Department of Natural Resources says 2025 was likely the smokiest year in five decades or more.
This story was originally produced by Minnesota Reformer, which is part of States Newsroom, a nonprofit news network which includes Wisconsin Examiner, and is supported by grants and a coalition of donors as a 501c(3) public charity.
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