This may be bur oak blight, a newly-recognized fungal disease in Minnesota that is usually seen in late summer to fall.  It also could be oak wilt.  Compare the photos and descriptions in the attached links to what you are seeing to make a more accurate determination.  A certified arborist can help you identify the issue, or you could send a sample to the plant disease clinic at the U of Mn.  See https://pdc.umn.edu/



https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/oak/leavesbrownedges.html
https://www.dnr.state.mn.us/treecare/forest_health/bur-oak-blight/index.html