St. Marys River (Michigan–Ontario) St. Marys River (Michigan–Ontario) The St. Marys River (), sometimes written as the St. Mary's River, drains Lake Superior, starting at the end of Whitefish Bay and flowing southeast into Lake Huron, with a fall of . For its entire length it is an international border, separating Michigan in the United States from Ontario, Canada. The twin cities of Sault Ste. Marie, Ontario, and Sault Ste. Marie, Michigan are connected across the St. Marys River by the Sault Ste. Marie International Bridge. The St. Marys Rapids are just below the river's exit from Lake Superior and can be bypassed by
Sault Ste. Marie, Michigan are cooler than nearby land areas. This tends to stabilize the atmosphere, suppressing precipitation (especially showers and thunderstorms) somewhat, in May, June and July. In autumn, the lakes are releasing their stored heat from the summer, making them warmer than the surrounding land, and increasingly frequent and strong polar and Arctic air outbreaks pick up warmth and moisture during their over-water passage, resulting in clouds and instability showers. In Sault Ste. Marie, this phenomenon peaks in September and October, making these the wettest months of the year. Also noteworthy is that in Sault Ste. Marie, the year's third wettest month,