Today is the winter solstice, the shortest day of the year in the Northern Hemisphere. Here in Fargo-Moorhead, we have a mere eight hours and 31 minutes from sunrise to sunset.
Your calendar likely says today is the first day of winter, which it is: astronomical winter. This period from the winter solstice to the vernal equinox is when the sun, as well as the night stars and constellations are in their winter positions.
What it is not, however, is the beginning of the winter weather season. Our weather has been quite wintry for well over a month already this year.
Weather certainly has seasons. Our very lives depend on the annual march of the seasons which vaguely follows the astronomical position of the sun in the sky.
However, weather is highly variable in a complicated way.
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In winter, for example, the minimum amount of solar radiation received at any point in the Northern Hemisphere is on the winter solstice. Yet in Fargo-Moorhead weather history, the coldest day of the year has occurred anytime from late November through mid-March. The first one-inch snowfall has happened as early as September and as late as March.
There is, of course, a general progression that is relatively similar from year to year. Historically, the coldest weather is most likely to happen in January and, likewise, the hottest weather is most likely in July. Notice that, in both cases, these average peaks and valleys of hot and cold happen several weeks after the peaks and valleys of incoming solar energy.
This lag of the meteorological seasons from the astronomical seasons is due to the fact that it takes time for things to heat up and cool down. Water is particularly slow to change temperature, which is why the Atlantic hurricane season peaks in September, a full two months after the strongest incoming rays have hit the water. This is also why Minnesota lakes are usually warmest in August and have the thickest ice around the first of March.
Meteorologists and climatologists often use specific three-month periods to compare the weather and seasons from one place to another. For these purposes, the months of December, January and February are used to approximate the winter season. But winter conditions should not be expected to magically start Dec. 1 any more than on Dec. 21.
The winter solstice happens this afternoon at precisely 4:53 p.m. CST. So when is the actual start of winter?
The answer to that is in your own mind. When winter gets you in its grip, then it is winter. This is something that varies from person to person as well as from year to year. There can be no official "first day of winter," and it certainly is not today.
