Smoke from wildfires in Canada and Minnesota is blanketing large portions of the Midwest and Northeast, triggering air quality alerts as officials warn millions of Americans to limit time outdoors.

The smoky conditions are expected to persist through Thursday, with forecasters warning that unhealthy — and in some locations hazardous — air could stretch from the Upper Midwest to the East Coast.

Minnesota remains one of the hardest-hit states as wildfires continue burning in its northeastern region. An air quality alert is in effect through Friday for Minneapolis-St. Paul, Alexandria, Two Harbors, and other communities.

Gov. Tim Walz on Wednesday extended Minnesota's peacetime emergency for 30 days as crews continue battling the fires, according to CBS Minnesota.

The smoke has also prompted alerts across neighboring states.

Michigan's environmental agency placed the entire state under an air quality alert Wednesday because of fine-particle pollution from the Canadian wildfires, while Wisconsin officials cautioned that smoky skies and poor air quality could linger for several days.

The haze has spread into the Northeast as well.

New York City is under an air quality alert through Thursday, while counties across western and central New York remain under air quality advisories.

Massachusetts issued a statewide alert after thick smoke turned skies over the Boston area a hazy brownish-yellow, and residents in parts of Maine also reported unusually discolored skies.

"A large smoke plume is moving across the area today, with more [smoke] expected south of the mountains," the National Weather Service in Gray, Maine, said Wednesday on X. "You can even see the smoke on the satellite!"

Tyler Hasenstein, a meteorologist with the National Weather Service in Chanhassen, Minnesota, told CBS News that the heaviest smoke is expected to spread across portions of the Midwest and East Coast, including Detroit, Milwaukee, northern Pennsylvania, and coastal New England.

According to Hasenstein, the thickest smoke could reach as far south as Washington, D.C., by Thursday.

Experts say dry weather has intensified this year's wildfire season.

Dan Westervelt, an associate professor at Columbia University's Climate School, told CBS severe drought and hot weather have created "a perfect storm for really dry conditions to provide a lot of fuel for these wildfires to burn."

Health officials are urging residents — particularly children, older adults, and those with heart or lung conditions — to avoid prolonged outdoor activity while smoke levels remain high.

They recommend keeping windows closed, running air conditioning or air purifiers when possible, and wearing an N95 mask if spending extended time outside.