As many weather-minded people may know, Groundhog Day occurred Saturday (Feb. 2), when winter's fate is decided by a groundhog's perception of its shadow. But in actuality, winter's midpoint in the Northern Hemisphere occurs today: Super Bowl Sunday.
According to folklore, if it is cloudy when the groundhog Punxsutawney Phil emerged from its burrow on Saturday, it would leave the burrow, signifying that winter will soon end. If it is sunny, the groundhog will supposedly "see its shadow" and retreat back into its burrow, and winter will continue for six more weeks. But Phil did not see his shadow early Saturday, suggesting an early spring is right around the corner.
Saturday was also Candlemas, once regarded as the first of the four "cross-quarter" days of the year or the middle of the winter season, halfway between the December solstice and the March equinox.
The true midpoint of winter, however, will occur today at 6:07 p.m. EST (2307 GMT), just 23 minutes before kickoff of Super Bowl XLVII. Although the altitude of the Sun has been slowly climbing and the length of daylight has been increasing since the winter solstice on Dec. 21, any changes up to this point have been relatively subtle.
For example: On the first day of winter at Portland, Maine, sunset occurred at 4:07 p.m. and the length of daylight (from sunrise to sunset) reached a minimum of 8 hours and 57 minutes. On "Super Sunday" – winter's midpoint — the sun will set at 4:55 p.m. with only 64 additional minutes of daylight having accumulated since Dec. 21. [In Images: Extreme Weather Around the World]
But as an old and true New England proverb notes: "As the days lengthen, the cold strengthens." And as most people who live in the United States, southern Canada and much of Europe will attest this particular winter season, the thermometer appears to be reluctant to respond to the increasing solar altitude. Indeed, that extra hour of daylight is not enough to give us any sense of warmth; while the days have gradually become longer, the bitterness of winter with its attendant ice and snow is still the same.
Still, it's in the second half of winter that the effects of the northward shift of the sun's direct rays start becoming much more noticeable. In fact, by March 20 — the date of the vernal equinox — the length of daylight will have increased by 2 hours and 19 minutes since Feb. 3. And because daylight saving time begins on March 10 this year, by March 20, the sun will be setting just seven minutes shy of 7 p.m.
Interestingly, for many northern locales, long-term records indicate the first four days of February are the coldest of the winter. But average daily temperatures rise rapidly thereafter, so that by the last week of the month they are higher than any day in January. Meteorologists, in fact, consider that the winter season is over at the end of February; they consider "meteorological winter" to be defined by the three coldest months of the year: December, January and February.
So for all those winter weary souls, take heart: In the days and weeks to come, you’ll more readily be able to sense the greater amounts of daily light and see the more northerly position of the afternoon sunsets on the horizon. And soon the weather will correspondingly respond as well.
So, take heed that while "Super Sunday" marks the halfway point of winter, that we’re also about to turn the corner so to speak, both astronomically and meteorologically. And regardless of what your local groundhog or woodchuck forecast early on Saturday morning, spring is well on its way.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.
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