September in northern MN is typically in the 60s during the day and 50s at night. Expect a windchill since it's right off the big lake.
The North Shore is a special spot because it is on Lake Superior, the lake that has become home for us. Between Graham spending two months out of the year in MN and Tia getting to explore the area while visiting, it has almost become a 'home away from home'. It's magical to think that The North Shore, though 7 hours from Marquette, is on the same BIG lake.