When first day of winter arrives depends on your point of view

first day of winter

The first day of winter arrives on either Dec. 1 or Dec. 21, depending on whether you are a meteorologist or an astronomer. Image: CC dcwriterdawn/Flickr

Did you know the first day of winter actually arrives on two different dates? “Meteorological winter” and “astronomical winter” are different technical interpretations of when the season begins. But for most people, the first day of winter arrives with a snow shovel and a harrowing commute.

First day of winter 2010

The first day of winter 2010 is Dec. 1 from a meteorological standpoint. The first day of astronomical winter is the winter solstice, which is Dec. 21 on the 2010 calendar. Winter didn’t wait for any human definitions this year. As of Dec. 1, a great deal of the U.S. had already experienced a few weeks of big snowstorms and sub-zero temperatures. The primary influence on winter weather this year is a phenomenon called La Nina. La Nina is a drop in ocean temperatures across the equatorial Pacific. La Nina brings harsh winter conditions across the northern U.S.

First day of winter arrives twice

On Dec. 1, meteorological winter began when northern hemisphere entered its coldest period of average temperatures. The coldest weather corresponds with the shortest days, beginning in November and extending through January. The coldest temperatures of meteorological winter can be expected in January, when the snow pack has a maximum cooling effect on the atmosphere. Astronomical winter will begin on the Dec. 21 solstice, the shortest period of daylight in the northern hemisphere. After the solstice, days start getting longer going forward and meteorological winter’s days are numbered. But astronomical winter continues until the vernal equinox, which will be March 21 in 2011.

Winter weather 2010-11

In real life, the first day of winter comes too early and the first day of spring comes too late for those living in the climates most affected by weather and short daylight. Winter 2010-11 will hit hardest in the Northwest, Great Plains, Great Lakes and New England, according to accuweather.com. Above normal snow and ice is in the forecast for these regions. For relief, consider going south. A “non-winter” is predicted from California to the Southeast.

Sources

Archeoastronomy.com

Accuweather.com

Wikepedia

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