The month of December normally starts cold and ends even colder. It’s the month with the shortest days and the most cloudiness.
The average high and low at the National Weather Service office near Negaunee on December 1 is 31 and 18. By New Year’s Eve, the average high and low drops to 23 and 10.
Decembers have been mild the last four years. The last below average December was 2017 when an arctic surge during Christmas week led to the month coming in over four degrees below average. This December has the potential to end below average.
The reason? Very strong upper-level high pressure is building over much of the arctic. When “blocking” high pressure develops over the arctic, cold air is forced to the south into the United States.
It appears we’ll have the first real surge of cold during next week. High temperatures may stay in the teens on a couple of days.
As for snow, no major storms are expected, though lake-effect snow off Superior is a certainty.
December will be cold, at least while the arctic block holds in place. However, there is a high probability of an overall mild winter. That’s because November will end “very warm” — over three degrees above average.
Over the last 100 years, there have been 27 “very warm” Novembers. A cold winter followed only once–during the winter of 1981-82.
Karl’s 5-day forecast