The largest recorded flood due to rain occurred on the Ontonagon River system August 21 and 22, 1942. The oldest residents of Ontonagon could not remember a more violent rainstorm. Roads were washed out, bridges flooded over and three people were drowned during the raging torrent.
The three people killed were swept to their deaths while they slept. A flash flood estimated at 10 to 12 feet deep tore down the valley occupied by a branch of the Ontonagon River. The victims, George Dent, 79, Tommy Mason, 31 and Joseph Paul Garsanki, 53, had no chance to escape as their creek-side cabin was stripped off its foundation and sent downstream. The 39-by-36 foot structure struck a bridge. The roof of the house came to rest on the bridge, while the rest of the building, including furniture, was smashed to bits.
A portion of Highway 45 north of Bruce Crossing was washed away. In Ontonagon, the large cement bridge over the river was in danger of being wrecked, as floating debris completely blocked river channels. The tremendous amount of water forced through the west channel undermined the west pier, so that the western third of the bridge began to sink. When that portion of the bridge was down almost two feet, cars were kept off.
This flood was unusual in that it occurred solely due to rain. Most Ontonagon River floods are caused by snowmelt and resulting ice jams. Serious 20th century ice jam flooding occurred in 1912, 1923 and 1963.
The pattern that brought the heavy rain featured a general westerly flow aloft with a strong ridge to our southeast (Image 2 above). The pattern forecast to develop over the next week bears some resemblance to the one 71 years ago (Image 3). However, the strong ridge is centered to our southwest instead of southeast. Nonetheless, Upper Michigan will be in the â??Ring of Fireâ?? zone, which means weâ??ll be subject to periods of thunderstorms. HPC, a division of NOAA, forecasts big rains centered on the west end of Lake Superior over the next week (Image 4).