Rare 'Maroon' Air Alert Now In Effect For Twin Cities

MINNEAPOLIS, MN — The Twin Cities metro and most of Minnesota is under a rare "maroon" air quality alert, the most severe tier on the index, as wildfire smoke from northern Minnesota pushes south.

The Minnesota Pollution Control Agency's air quality index hit 310 for fine particle pollution Thursday, landing in the hazardous, or maroon, category. Ozone was measured at a moderate 67.

Friday's forecast improves slightly to unhealthy for sensitive groups for particle pollution, with ozone staying moderate.

The MPCA expects conditions to clear to good on both measures by Saturday.

The agency says a frontal boundary pushed heavy smoke further south and west starting Wednesday afternoon, with a rapid onset made worse by the ongoing heat.

The alert covers northern, central and portions of southern Minnesota through 11 a.m. Friday, though heavy smoke could linger longer in the northeast.

Rain near the fires Friday could cut smoke output and speed up improvement, but the MPCA says uncertainty is high.

A cold front is expected to bring cleaner air to the rest of the state on northwest winds by Friday.

In hazardous conditions, sensitive groups, including people with lung or heart disease, children and older adults, should remain indoors. The general public should avoid any outdoor exertion.

Roughly 17 lightning-caused fires are burning across the Boundary Waters Canoe Area Wilderness in northeastern Minnesota, covering an estimated 55,000 acres and mostly still at 0 percent containment, with the two largest, Thumb Fire and Bear Trap Fire, each over 13,000 acres and burning near or across the Canadian border.

Rangers evacuated an estimated 6,000 to 10,000 campers from the 1.1 million-acre wilderness this week, with about 90 percent out by Wednesday and no injuries or deaths reported.

The fires, combined with a severe heat wave, have pushed smoke as far as Toronto, New York, and potentially Washington, D.C.

Officials warn some fires could keep burning for months, until snowfall.

Reporting from the Associated Press was used in this story.