Winter Weather in Big Snow Country: a lot of Snow but Little Extremely Cold Weather

The true Northern style winter is about 4 months long, from about November 20 until about March 20. But winter can be up to 4 1/2 months long in a more severe than usual winter. On the other hand, global warming may produce some winters that are effectively shorter, down to say 3 1/2 months.

Global warming can possibly extend a mix of rain and light snow well into December, as it did in two recent years. If this happens, since a normal December by itself produces on average 1/4 of annual snow, the overall snow for the year will most likely end up to be much less than usual.

In almost all years, at least 90% of the snow falls between November 20 and March 20. It snows much more in the first two of those four months. The average date when half of all snow for the season has fallen is no later than January 10. The rate of snow drops off by half or more whenever Lake Superior becomes substantially frozen over, which it often but not always does between very late January and early February.

For how much snow falls and typical snow depths, see this article.

COLDEST MONTHS OF ALL
During much of the coldest two months of winter, running from December 25 until about February 25, the temperature remains at or below freezing 24 hours a day, which causes the snow to pile up much more than it would if there were a good number of days above freezing. During these coldest 60 days, you typically will get only about eight days when the temperature reaches 33 degrees or higher.

In a colder than normal January, it will rise above freezing (32 degrees) during the day only one or two times the whole month. In a normal January, the high temperature will be a little above freezing three or four times on the average. Except in a really cold January, there will be at least one day in January when the high temperature is at least 40, but rarely will a January day be any warmer than 42.

The temperature remains below freezing all day more than 75% of the days during most December-February periods. In typical winter months, the temperature will rise above freezing between three and five days during January and during February, and five or six days in December, mostly in the first half of December.

THE THREE COLDEST MONTHS: DECEMBER--FEBRUARY
Everyone knows there is a lot of snow in the winter in Big Snow Country. What most people don't know is that in the winter it is actually a little warmer here than it is south and west of here. The overall average winter temperature in Big Snow Country (December through February) is about equal to the average winter temperature in Minneapolis-St. Paul, which is 200-300 miles southwest of Big Snow Country. Most people don't know this and would not think it to be true. The overall average winter temperature in both the Twin Cities and in Big Snow Country is about 17 degrees.

Even more surprising is that the most severe cold snaps are actually substantially worse in the Twin Cities than they are in Big Snow Country. This is because Lake Superior modifies even severe cold to make it somewhat less severe. In the most severe cold snaps, happening between once and three times a year, the temperatures in the Twin Cities will be about four or five degrees colder than they are in Big Snow Country. The more minor cold snaps are going to be a degree or two worse in Minneapolis-St. Paul than they are in and Big Snow Country.

THE COLDEST WEATHER OF ALL
The most extreme cold periods happen either once, twice, or if you are not lucky three times between late December and the first few days of March. These outbreaks of true arctic air in Big Snow Country cause the day highs to be between zero and ten above zero, and the night lows to be between fifteen below and five below. These outbreaks last from two to six days.

These cold waves are not as severe as they are more than 30 miles from Lake Superior. These cold periods are from 3-25 degrees less extreme in Big Snow country than they are in all of Minnesota, than they are North and South Dakota, and than they are in all of Wisconsin except for right along the Lake Michigan shore and except for the southeast area.

Looking more generally at all winter days that are below normal, within 30 miles of Lake Superior, the nights are substantially warmer (5-25 degrees) while days are between 15 degrees warmer and 5 degrees colder than they are in those other areas.

THE ABSOLUTE COLDEST NIGHTS OF THE YEAR
The coldest handful of nights / mornings of the year are never as severely cold in Big Snow Country as they are away from the lake. To be specific, unlike in the Dakotas, unlike in Minnesota including the Twin Cities, and unlike in Wisconsin away from Lake Michigan, the temperature in Big Snow Country drops below minus 10 degrees only between once and four times a year. You can count on mornings of less than minus 10 three to fifteen times per year in those other areas.

In most years, the temperature never drops below minus 15 degrees in Big Snow Country, whereas it can easily drop to minus 20, to minus 30, or even to minus 40 (North Dakota) in those other areas.

So it is quite rare for the temperature to ever drop below minus 15 degrees. The absolute coldest night / morning of the year will most years end up being between minus 11 and minus fifteen degrees, which is about 5 degrees WARMER than the usual coldest night /morning in the Twin Cities.

MEDIAN ABSOLUTE COLDEST DAY OF THE YEAR IN BIG SNOW COUNTRY: NOT THE AVERAGE TEMPERATURES BY ANY STRETCH!
The first number is the average morning low of the coldest day of the year and the second number is the average afternoon high.

Copper Harbor -8/3
Calumet-Laurium -13/1
Houghton -14/1
South Range-15/1
Painesdale -16/1
Ontonagon -10/3
Ironwood -16/2
Marquette -15/3
Munising -15/3

FOR COMPARISON
Twin Cities, Minnesota -20/0
Wausau, Wisconsin -18/0
Fargo, North Dakota -25/-5
Winnipeg, Canada -33/-13

THE SHORE VERSUS 5-30 MILES INLAND ON THE COLDEST 2-3 MORNINGS OF THE YEAR
On the coldest mornings of all, the night / morning lows are going to be about four degrees colder at Houghton than they are at Copper Harbor. Specifically, in the most severe arctic waves, which normally occur once or twice a year, at Houghton the lows will be between -10 and -15, whereas the lows at Copper Harbor will hold to between -6 and -11. In slightly higher terrain south of Houghton, at South Range for example, the coldest mornings of the year will be between -12 and -17. To the southwest, the coldest mornings of the year are slightly colder due to specific topographical features. There you can look for the coldest mornings to be between -13 and -18 at Ironwood and between -15 and possibly -20 at Wakefield.

Meanwhile, at Marquette lake shore, the coldest mornings of the year are going to be between -10 and -15 degrees. The coldest mornings of the year are up to three degrees colder 5-10 miles inland (-13 to -18) and another degree colder still by the time you get to Negaunee (-14 to -19). Michigamme, the principal town in western Marquette County is in a higher, farther from the lake, semi-wilderness area where the coldest mornings of the year are between -18 and -23 degrees.

BIG SNOW COUNTRY COLDEST 2-3 NIGHTS / MORNINGS OF THE YEAR
The coldest night of the year will often feature morning lows in the following range:

Copper Harbor -6 to -11
Calumet-Laurium -10 to -15
Houghton -10 to -15
South Range-11 to -16
Painesdale -12 to -17
Ontonagon -7 to -12
Wakefield -15 to -20
Ironwood -13 to -18
Champion -17 to -22
Negaunee -14 to -19
Marquette lakeshore -10 to -15
Marquette inland area -13 to -18
Munising -10 to -15

COLDEST NIGHTS / MORNINGS ELSEWHERE
Big Snow Country is the counties along Lake Superior in Michigan. Just to the south of Big Snow Country, the coldest mornings are much colder. For example, at Iron Mountain MI, expect the coldest two or three mornings of the year to be between -20 and -27 degrees. More comparisons:

WISCONSIN COLDEST 2-3 NIGHTS / MORNINGS OF THE YEAR
Rhinelander -18 to -25
Wausau -15 to -22
La Crosse -14 to -21
Madison -11 to -18

MINNESOTA COLDEST 2-3 NIGHTS / MORNINGS OF THE YEAR
International Falls -29 to -36
Duluth -17 to -24
St. Cloud -19 to -26
Twin Cities -14 to -21
Rochester -14 to -21

NORTH DAKOTA COLDEST 2-3 NIGHTS / MORNINGS OF THE YEAR
Grand Forks -24 to -31
Fargo -20 to -27
Bismarck -20 to -27

SOUTH DAKOTA COLDEST 2-3 NIGHTS / MORNINGS OF THE YEAR
Aberdeen -18 to -25
Huron -16 to -23
Sioux Falls -12 to -19

MANITOBA COLDEST 2-3 NIGHTS / MORNINGS OF THE YEAR
Winnipeg -27 to -34

DAILY AVERAGES AT HOUGHTON-HANCOCK
You can see the exact average highs and lows for Houghton-Hancock for every day of the year. You will find them here.

For details about the weather between March 20 and November 20, see this article.

Lake Superior ice and how it Effects Snowfall

LAKE SUPERIOR ICE COVER
The more Lake Superior is covered with ice, the less lake effect snow there will be. In the last 30 years, apparently due to global warming, the Lake has been on average less covered with ice which has, as expected, led to more lake effect snow.

Global warming has apparently led to less ice cover on Lake Superior and thus more snow in Big Snow Country. However, there is evidence that climate variation over any 100 year period, regardless of and apart from any overall global warming, has played an even bigger role in determining the actual snowfall in Big Snow Country. It seems that across many decades, how cold it gets on average in the winter has varied in patterns (or waves) lasting about three decades each, completely separate and apart from overall global warming.

So far, extra snow from global warming alone would hardly be noticed on top of all the snow that falls with or without global warning. Assuming that global warming is real, it is apparently true that global warming has already led to an increase of roughly 10% in the snowfall in Big Snow Country.

Historical evidence indicates that from about 1860 until about 1980, Lake Superior most often was completely iced over for at least several miles out, for the first few miles from the American southern shore, by the holiday season: the last week of December. Since 1980, it has more and more taken almost three weeks longer than that for the shore area to ice over, until about the middle of January.

From 1860 until about 1980, Lake Superior ice cover near and along the southern shore usually melted away as of the middle of April, by the 20th of April at the latest. Since 1980, the near shore ice cover has been on average melted away almost three weeks sooner, by about the end of March.

The Lake ices over from shallow water near the shore outward. In very severe winters, the Lake becomes almost entirely iced over, including even most of the middle of it. Such winters have become less common, although the 2008-09 winter defied recent history and was cold enough to be classified as a severe one. In a mild winter, which apparently is more likely now due to global warming, the Lake, even at peak ice, may be iced over only relatively near the shore, with greater ice cover further out into the Lake on the Canadian side than on the American.

Peak Lake Superior ice is reached during mid or late February. The greater the percentage of the Lake that is iced over, the slower it will melt. On the other hand, just like on land, melting increases from one week to the next during March and April. Late April "melting power" is probably 10 times early March "melting power.

In the century up until 1980, the Lake on average became almost half iced over by mid February, with the deepest waters well out from the shore (starting about 25 miles out) remaining ice free except in colder than normal winters. There was (and still is) quite a bit of variation in Lake Superior ice cover from year to year. During the 1880-1980 century, in the most severe winters, the Lake became up to about 90% iced over. In the most mild winters, the Lake became as little as 15% iced over (near the shores only.) Whether the ice has ever become literally 100% iced over is unknown.

There were patterns during the century for which there is some scientific information. In general, from about 1898 until about 1922, Lake Superior averaged substantially more peak ice coverage (in February) than the overall 45% average for the century. Then from 1922 until 1958, Lake Superior averaged substantially less peak ice coverage than the overall 45% average. From 1958 until 1982, Lake Superior peak ice coverage became substantially higher than 45% again. Since 1982, Lake Superior peak ice coverage has been substantially below 45% again.

From the foregoing and also from actual historical snowfall records, we know that:
1898-1922: Lake effect snow was less than the 100 year average, probably about 15-25% less judging from available recorded evidence.
1922-1958: Lake effect snow was heavy, probably about 15-25% more than the 100 year average.
1958-1982: Lake effect snow was less than the 100 year average, probably about 15-25% less.
1982-current: Lake effect snow was heavy, probably about 15-25% more than the 100 year average.

For example, consider Houghton. It has been averaging about 220 inches of snow a year over the last 30 years, within the low ice and heavy snow combination. If this snow is actually 20% higher than the 100 year average, then that 100 year average is about 183 inches, which is about what in fact it is. If the Lake were to again start largely icing over again at peak ice in February (which appears to be very unlikely despite the surprisingly cold 2008-09 winter) then Houghton's expected snowfall might be as little as 146 inches per year. Note that the swing caused by the high ice versus the low ice historical periods is such that the low ice periods produce about half again as much snow as do the high ice periods.

As we have just seen, since 1982, the percentage of the Lake surface that ices over at the peak has on average been substantially less than the century average of 45%. Open water is the original source of lake effect snow, not iced over water. The more miles of ice the clouds packing the lake effect snow have to travel over before reaching land, the more the snow will fall on the ice on the Lake, and the less the snow will fall on the land.

Big Snow Country is researching whether any scientist has yet discovered the relationship between lake snowfall and how many miles of ice there are between the open water and the land.

Find out how much ice cover there is on Lake Superior at this time here. Click on the map there to make it larger and readable.