Rain showers are pumping excess water into the Bitterroot River near Darby.
The south area of the valley has seen some flooding and Darby firefighters are preparing for more.
As the river swells it can get messy for homeowners who live near the river.
It's just starting to get some flooding, said Lenny Beiler.
On Wednesday, Beiler and a number of firefighters and volunteers were filling hundreds of sandbags to stave off flooding near the river.
Rain was coming down hard in spurts, and with all that rain, the threat of flooding increases.
"I think anybody living on the river is going to be affected," said Beiler.
He said on Tuesday night crews prepared about 100 bags.
Students who are off from school are also volunteering.
"We're trying to get ahead," said Beiler, "and filling up extra."
He said the department has sand stockpiled.