Weather Talk: Here's how Hettinger got to 45 below
In late December, on a night that was in the teens and 20s below zero over most of the region, the temperature in Hettinger, N,D,, reached 45 degrees below zero.
A few other stations across eastern Montana and western South Dakota also reported temperatures near 40 below. These anomalously low temperatures were, in part, due to a condition known as cold air damming.
The Arctic air blowing into the northern Plains was encountering the uphill slopes of the Rocky Mountains in Montana. Because the very cold and dense air was in a shallow layer near the surface, it was unable to rise up and over the mountains.
This effect caused very cold temperatures to pool in a few areas, which then drifted southeastward carried along underneath the center of high pressure. These extremely cold temperatures only occurred in a few spots where the air remained calm and undisturbed overnight.
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