Canadian wildfire smoke will once again engulf the entire state of Minnesota for about 48 hours, beginning early Thursday and lasting until late Friday.
Heavy plumes of smoke have been pooling and building up from fires in the Northwest Territories over the last several days and the shifting wind is pulling it all toward Minnesota, said David Brown, air quality meteorologist for the Minnesota Pollution Control Agency.
"It will get to northern Minnesota right at midnight, at the start of the day (Thursday), reach the Twin Cities sometime in the morning and blanket the entire state by the afternoon," Brown said.
For the 10th time this summer, the agency issued a red air quality alert for the Twin Cities and most of eastern Minnesota — meaning enough smoke and fine particles will be in the air to make it unhealthy for everyone. That's the most red alerts issued in a single summer since at least 2000, when the agency started tracking fine particles more consistently.
Air quality is only expected to be slightly better in western Minnesota. The smoke could cause serious health risks, especially to those with heart and lung conditions. Experts advise to stay indoors, or to wear a well-fitted N95 mask if that's not possible.
The Minnesota Department of Natural Resources said Thursday that it would not issue or activate any burning permits for as long as the smoke remains. Agency officials said that campfires are highly discouraged.
Strong winds throughout the day on Thursday will help a little, Brown said. But the wind is expected to die down on Friday morning.
"If we have several hours of light wind it could cause smoke to pool up. So Friday morning is probably when it will be at its worst," he said.
The air pollution this summer has been brutal throughout the Upper Midwest, mainly due to Canadian wildfires. Recent rain and cool weather has helped relieve some of the smoke coming from forests in Saskatchewan and Alberta that plagued Minnesota throughout May and June.
But for the past several months a heat dome has remained over the Northwest Territories, where a handful of fires continue, Brown said.
"We're past the halfway point of wildfire season in Canada," he said. "It usually goes to the end of September, but we've seen these kinds of fires in the Northwest Territories through October and into November before."
When the fires are raging, the smoke follows a familiar pattern. Cold fronts that come into Minnesota from the north typically bring smoke with them. When heatwaves follow winds from the south, the smoke typically clears.
Southern heat is expected to blow in to Minnesota late Friday.