The Yaak River in northwest Montana is already flooding, and water is approaching the foundations of some homes on the Thompson River. There are reports of water over the pavement on Montana Highway 35 south of Bigfork, where speed limits have been reduced to 35 mph between mile markers 22 and 23.5, and on Lower Lynch Creek Road near Plains.

And to the south, in the Bitterroot Valley, homes have deployed sandbags to divert the rising waters of Eight Mile Creek near Florence.

Just 30 feet from the edge of Eight Mile Creek, Mark Wilkins placed 160 sandbags around his home on Sunday.

"We've been here for 11 years and we've never seen anything like this," Wilkins said. "It's kind of eye-opening to see what the power of water can do."

Over the weekend, Eight Mile Creek went from about 15 feet across to something closer to 50.

"Without the sandbags, it would have been coming right through my house," Wilkins said.

By Tuesday morning, the Bitterroot River could reach flood stage at Darby and Bell Crossing, the Weather Service advised. On Monday, the river was at 6.9 feet in Darby; flood stage is 7.5 feet. At Bell Crossing, the Bitterroot reached 10.2 feet at midday Monday; flood stage is 11.0 feet.