As Canada grapples with one of its worst wildfire seasons on record, smoke from the blazes have prompted air quality alerts across the U.S.

Canada is battling more than 700 active wildfires across the country, roughly two-thirds of which are burning out of control, according to the Canadian Interagency Forest Fire Center (CIFFC). Smoke billowing from the blazes has blanketed central Canada and the northern U.S., prompting widespread air quality alerts.

Canadian wildfires burning across northern Manitoba and Saskatchewan are sending smoke through central Canada, the Great Lakes region and the northeastern United States, reducing air quality and visibility in major cities. Forecasters said they were “optimistic” that the lingering wildfire smoke would ease later in the day on Tuesday.

An air quality alert remains in effect for the entire state of Minnesota on Monday. Smoke from Canadian wildfires prompted the alert, which is set to expire at 9 a.m. Tuesday. The northern half of the state will likely see the worst air quality.

An air quality alert will be in effect for all of Minnesota until at least 9 a.m. Aug. 12, according to the state Pollution Control Agency.

Air quality forecast for August 11th from the MPCA predicts unhealthy air for everyone in the northern half of Minnesota.