<Tr> <Td_colspan="14"> Source #1: NOAA (relative humidity and sun 1961 − 1990) </Td> </Tr> <Tr> <Td_colspan="14"> Source #2: The Weather Channel </Td> </Tr> <P> Even though winter does not officially start until late December, Minnesota usually begins experiencing winter - like conditions in November, sometimes as early as October . As with many other Midwestern states, winter in Minnesota is characterized by cold (below freezing) temperatures and snowfall . Weather systems can move in from the north, west, or south, with the majority of the weather being driven in from the north . A vigorous jet stream brings high and low - pressure systems through in quick succession, which can cause large temperature variations over a short period of time . </P> <P> As the last remnants of summertime air in the southern U.S. start to lose their grip, cold polar air building up in northern Canada starts to push farther south, eventually spreading into Minnesota . By the time December and January arrive, Minnesota is fully engulfed in the polar air and is then subjected to outbreaks of arctic air masses . Because there are no natural barriers north or northwest of Minnesota to block arctic air from pouring south, Minnesota gets regular shots of the arctic air through the winter . High pressure systems which descend south from the Canadian plains behind the fronts bring light winds, clear skies, and bitterly cold temperatures . The northern part of Minnesota gets the brunt of the cold air . International Falls, sometimes called the "Icebox of the nation", has the coldest average annual temperature of any National Weather Service first - order station in the contiguous United States at 37.4 ° F (3.0 ° C). Tower, Minnesota, sinks below 0 ° F (− 18 ° C) on an average of seventy - one days per year, while the ten coldest counties in the contiguous US, based on January minimums, are all located in Minnesota . The air mass then slowly moderates as it moves south into the rest of the state . Alberta clippers alternate with these high - pressure systems, bringing high winds and some snowfall with them . </P>

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