Canadian wildfire smoke is triggering air quality alerts across the U.S. Midwest and Northeast on Thursday, as the northern nation’s boreal forests continue to burn at a rate not seen except for a historic season in 2023.

Maps show where new plumes of smoke will cause hazy skies through the end of the week. Low-level smoke is forecast to spread eastward Wednesday across the Appalachians and into the Mid-Atlantic and Northeast.

Smoke from Canadian wildfires is engulfing much of the eastern and central United States and and is expected to continue for days.