Thunder Bay is a bay in the U.S. state of Michigan on Lake Huron. The bay extends from North Point at 45°01?19?N 83°15?58?W? / ?45.02194°N 83.26611°W? / 45.02194; -83.26611 to South Point at 44°53?00?N 83°18?51?W? / ?44.883333°N 83.31417°W? / 44.883333; -83.31417.