Communities within the United States’ Great Lakes region will experience their highest air pollution levels throughout Sunday due to wildfire smoke from Canada, but National Weather Service forecasts show significant relief isn’t coming anytime soon.

Smoke has lowered air quality across the Midwest and Northeast to unhealthy and even hazardous levels over the past week as numerous out-of-control fires burn in Ontario, Manitoba and Saskatchewan. The total area burned surpassed historical highs on Thursday as peak fire season continues into late August.

Forecast models show near-surface smoke remaining throughout the Midwest and Northeast through at least Wednesday. Weather patterns are also expected to push smoke from Canada’s fires down southward into new Midwest and Western states in the coming days, including Colorado, Iowa, Kansas, Missouri, Nebraska and Wyoming.

The National Weather Service issues air quality alerts when levels of fine particulate matter, which are small particles that can penetrate deep inside lungs and are produced in large quantities by wildfire smoke, are elevated enough to pose health risks. Alerts are currently in effect for Illinois, Indiana, Ohio, Michigan and Wisconsin, but more alerts are expected to be issued in other states as the smoke pushes south.

“The heaviest smoke is currently in Wisconsin, where significant portions are at VERY UNHEALTHY levels, while most other areas are seeing UNHEALTHY to USG conditions,” the U.S. Interagency Wildland Fire Air Quality Response Program said in an alert on Sunday. “These conditions are expected to mostly persist today with the exception of northern Ohio and southeast Michigan, where Detroit and Cleveland should see conditions improve to MODERATE levels today.”