Extremely cold weather in western Montana has led to ice on the rivers and some concerns that it could cause back-up flooding.

"When you get into long periods of very cold temperatures, ice starts to form over the rivers in Western Montana," said National Weather Service Meteorologist Ray Nickless.  "We've seen that ice start to accumulate into a pretty significant amount of ice on the Clark Fork River, here in Missoula and especially in East Missoula, the river is pretty clogged up with ice."

Nickless says he has been monitoring the rivers for back-up flooding and, though there were some areas of concern, most water is finding its way into the river. He expects the ice to start thaw as temperatures rise this week.

"We seem to be having our coldest temperatures of the year in November these days," Nickless said. "Last year was very similar where we had an arctic blast in November, even a little bit earlier than this one and did the same thing, where it formed a lot of ice in the rivers and then we went into a long period of time where it wasn't all that cold."

The biggest hazards could come if there is an extremely quick thaw of the ice on the river, or if a lot of rain comes to the area in the near future. Back in 1996, Governor Marc Racicot declared western Montana a disaster area due to ice jams, but there was much more snow, and the temperatures back then dipped down to 20 below zero.