If you happened to notice a milky or hazy appearance to the sky today, you were seeing some smoke being blown into the region from wildfires in Arizona. The wildfires in eastern Arizona are some of the worst that state has seen. As the smoke plume rises and advects to the northeast, it has fanned out and spread into the Midwest and Great Lakes in the middle and upper parts of the atmosphere.
Here's a MODIS Aqua satellite image showing the forest fires in Arizona today:
Here is a zoomed out version of that MODIS satellite image showing the smoke fanning out over the central US:
Finally, here is a satellite shot from NOAA-NASA GOES Project showing the smoke plume over the Duluth area: