Weather Why: Temps below freezing, why isn't the Clark Fork frozen?

Clark Fork

Overnight lows on Wednesday dropped well into the negatives, with West Yellowstone seeing -31 degrees. Western Montana is in for another night of below-average temperatures.

Water is said to freeze at 32 degrees, but that’s not always the case.

While the Clark Fork River was showing signs of freezing, it’s still not frozen completely. That’s because it’s moving.

It’s hard to give an exact number as far as temperatures go, but the movement of the water makes it harder for ice molecules to stick together. Once the first few molecules manage to form, a full-on river freeze is much easier.

Before Wednesday, Missoula had not seen single-digit temperatures since Feb. 23. However, Missoula has seen its fair share of cold days. The coldest December days were back in 1964 and 1983, when lows dropped down to -30 degrees.

Once rivers and ponds begin to freeze, it’s important never to walk on frozen water and to keep pets and children far away.

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