Flood in Flathead County, Montana

Widespread high water affected the Flathead River basin. Anticipating heavy rainfall, operators at the Hungry Horse Dam opened the spillway gates at 1137MST on May 28 to manage reservoir capacity, causing significant downstream rises. On Friday morning, May 28, the City of Columbia Falls temporarily closed the back portion of River's Edge Park to the public due to early inundation. The Flathead River at Columbia Falls (CFMM8) crested at 13.78 feet with a discharge of 46,400 CFS on the evening of May 29, remaining above the minor flood stage of 13.0 feet. A subsequent NWS flood survey on June 1 at 1025MST documented high water completely surrounding private residential properties near the confluence of the South Fork and Middle Fork of the Flathead River. Floodwaters fully encircled a home 1 mile west of Hungry Horse, though the water had not yet breached the structural foundation or entered the living spaces at the time of the inspection.

Between May 28 and June 4, 2026, a very slow-moving upper-level low-pressure system over Montana tapped into moisture from the Gulf of America, bringing heavy and widespread precipitation to western Montana. Prior to this event, several locations had already received significant moisture in May, leaving soils saturated and mountain runoff elevated. The combination of intense rainfall and ongoing snowmelt led to swollen rivers, and overwhelmed small streams, and flooded local irrigation canals. Intense thunderstorms brought heavy rain-rates in Sanders County resulting in mudslides.