Moist Pacific air could drop as much as an inch of water on Billings in the next two days, exacerbating flooding conditions across the area.
The National Weather Service has issued a Winter Weather Advisory and a Flood Warning in south-central Montana.
Streams and rivers, already running high, could see as much as half an inch of rain and 3 to 6 inches of wet snow over the next two days.
Do not cross roads with flowing water moving across them, the advisory said.
People in flood-prone areas should be on high alert for signs of flooding. If flooding is sighted, contact the proper authorities, the warning said.
The Winter Weather Advisory is in effect from Monday at 3 p.m. until Tuesday at 3 p.m.
The Flood Warning is in effect until expiring at 7:45 a.m. Wednesday.
Rain may begin Monday at 1 p.m., and transition to snow by evening. Less than half an inch of snow is likely. The high will near 44.
Lows will approach 28 Monday night, as 4 inches of snow continues to fall.
Half an inch of snow is possible Tuesday, but snow should diminish by afternoon. Highs will approach 39.
The likelihood of precipitation will be all but gone by Tuesday night, as skies become partly cloudy and lows fall to 27.
Skies may be sunny Wednesday, with a high of 48.