The National Weather Service (NWS) in Duluth reports on Twitter that an early fall frost is likely:
Patchy frost is possible for portions of Northland Thursday night into Friday morning, especially where skies are clear. Folks near Lake Superior and further west in Minnesota (Walker to Brainerd area) are unlikely to see any frost.
The NWS Duluth website says a cold front moving in is likely to drop temperatures significantly, delivering cold rain in advance. As a result, the NWS forecasts cooler temperatures for the region from Thursday into the weekend: