Since this is such a popular fall destination, thought I'd post this. I just spent the weekend camping at Tettegouche. We hiked up to Carlton Peak in Temperance River State Park and the maples on mountains looking west (away from the shore) had lots of color, albeit subdued. Considering the cool nights they're having, they seem to be peaking 1-2 weeks early.
HOWEVER, note that there was very little change along the shoreline, if the trees had leaves at all. And that those colors are more the yellows/browns due to the tamaracks, aspens & birches.
There also were some great pockets of color between Hinckley & Duluth, more going south on the highway instead of north (not sure why).
The days were warm and sunny, the nights cooled off fast. No hard frost yet, but lots of freeze warnings starting to happen. Also, there's a nasty stretch of construction for about 8 miles around Banning State Park. Not sure why, but heading south on I35 was painfully stop and go Sunday, so you may want to time your drive to miss the worst of the backup.