The Most Notorious Floods in Montana History

Montana’s Most Notorious Floods: A Look Back at Our Worst Water Events

Montanans count themselves lucky when it comes to natural disasters. We don’t worry much about hurricanes, tsunamis, or tornadoes. Wildfires? Sure—those are part of life here. Earthquakes are rare, too, with the most significant being the 1959 Hebgen Lake 7.5 quake that formed Quake Lake.

Flooding, though infrequent, can be downright disastrous when it happens.

Most of Montana falls into a semi-arid climate, meaning moisture is usually limited. But sometimes, the right (or wrong) mix of snowpack, rain, and rapid warming creates historic flood events. According to the National Weather Service, here are five of the worst on record.

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1908 Flood

While the Wright brothers wowed the world with flight, Montana was underwater. A cool, soggy spring dumped up to 12 inches of rain across Gallatin, Park, Carbon, Sweet Grass, and Cascade counties. By June, rivers burst their banks and railroad tracks vanished under floodwaters.

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1948 Flood

May rains followed by hot temps led to massive snowmelt. The Clark Fork near Plains surged to a record 134,000 cfs. Damages west of the Divide reached $3 million (more than $40M in today's money), and the Missouri and Sun River basins also saw major flooding.

1964 Flood
With up to 10 inches of rain falling in just 36 hours, this event is considered one of the worst floods in Northern Rockies history. The Marias River near Shelby crested at a staggering 241,000 cfs.

1978 Flood
After May dumped 15–32 inches of snow in parts of Montana and Wyoming, the Yellowstone River exploded. Miles City hit 102,000 cfs, and 19 counties were declared disaster zones. Total damages topped $33 million.

2011 Flood

From ice jams to spring melt, 2011 saw flooding nearly everywhere. The Musselshell River near Roundup was especially hard hit, spilling into homes, farmland, and infrastructure across the region.

So far this spring, most of Montana has been spared from any major flooding. However, as temperatures climb throughout June, we can expect water levels to be high as spring runoff continues.