This story was updates Thursday morning as the Wisconsin DNR extended the air quality advisory.
The Northwoods had among the worst air quality levels in the world Wednesday.
At their peak, air quality monitors in Ironwood and Crandon showed the PM 2.5 level exceed 600. PM 2.5 is fine-particle air pollution.
The ‘Hazardous’ level is between 301 to 500 PM 2.5. There is not level above that.
At these levels people are encouraged to stay indoors. Children, elderly, and those with underlying health conditions like asthma or heart disease are most at risk.
The smoke is coming from dozens of wildfires burning across northern Minnesota and Ontario. The fires burning Superior National Forest have led to the closure of the Boundary Waters.
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It is difficult to accurately forecast smoke more than 24-48 hour out.
The Wisconsin DNR extended the air quality advisory Thursday morning until noon on Friday. The air quality is expected to stay in the unhealthy to hazardous range.
A southerly wind on Friday should push the smoke out of the state.
"At that time, it will be possible that we will extend the advisory once again for eastern areas, especially those impacted by Lake Michigan," the DNR said in the advisory. "It is also possible that areas along Lake Superior will see prolonged smoke impacts and need to remain in the advisory. However, we expect to remove much of the state from the advisory area at that time for this first round of smoke."
Smoky summers have become more frequent for the Northwoods in recent years.
You can find resources on knowing your risk, ways to reduce smoke impacts, and get the latest air quality on the EPA’s AirNow website.
