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DNRC Headquarters
1539 Eleventh Ave. Helena, MT 59601
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Ice jam potential is greatest in February, March

HELENA, Mont. – Damaging floods caused by ice jams are a fact of life along many Montana rivers and streams. And while the winter of 2019 has been mild so far, the Montana Department of Natural Resources and Conservation (DNRC) would like to remind residents that February and March have the greatest potential for ice jams, and conditions can change rapidly.

“Montana experiences the highest number of reported ice jams in the continental US, with most occurring in February and March” said DNRC Director John Tubbs. “Flooding can happen in any community and it can happen quickly. Residents in flood-prone areas should take steps to safeguard their families and property.”

Arin Peters, Senior Service Hydrologist with the National Weather Service Great Falls, has advised that the thick ice associated with ice jams forms when temperatures are consistently low for extended periods of time.

Worby McNamee, a DNRC floodplain specialist, said it’s important that residents living near a river or stream develop a flood evacuation plan and consider the following steps:

 Purchase flood insurance. In most cases flood insurance must be purchased 30 days before a flooding event.

Keep extra drinking water on hand. Flooding can compromise local water systems.

Shovel or plow snow away from homes and structures.

Be ready to transport valuables or, where practical, elevate them.

The Montana All-Hazards Weather Monitor web site offers up-to-date information on stream flows and potential flood conditions:

To learn more about the National Flood Insurance Program, visit

More than 80 percent of ice jams and associated flooding in Montana take place between January and March, with the highest number occurring in March. The most ice jams ever recorded in a single season was 75 in 1996.