When is the official start of winter? Here's why meteorological winter begins on December 1
Massive winter storm slams Midwest
A major winter storm blasted parts of the Midwest and the Central U.S. this weekend with heavy snowfall, causing travel nightmares for millions of people as they return home from Thanksgiving plans.
Many across the Northern Hemisphere have different opinions about when winter officially begins. Yet meteorologists have remained consistent about when the season actually starts in December.
Calendars found in homes across the country usually say winter begins on Dec. 21, when in reality the season starts three weeks earlier on Dec. 1.
Meteorologists and climatologists define the seasons based on when temperatures typically change, not on Earth’s rotation.
According to the National Oceanic and Atmospheric Administration (NOAA), the length of meteorological seasons is more consistent than that of the astronomical seasons, ranging from 90 days for the winter of a non-leap year to 92 days for spring and summer.
Scenic shot of heavy snowfall in Chicago. (Robert Ray / FOX Weather)
Under the meteorological season scheme, the four seasons are each allotted three months, making it easier to calculate and compare weather conditions in recent years.
The difference with astronomical seasons is that the start of winter and summer is based on whether the North Pole is oriented toward or away from the sun due to Earth’s natural tilt.
The astronomical change of seasons is marked by either a solstice or an equinox, according to NOAA. When the Earth’s axis isn’t tilted in favor of either direction, it is referred to as an equinox or the start of spring or fall.
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The rotation of Earth around the sun and the planet’s tilt are the basis for the astronomical calendar.
NOAA says the meteorological seasons were created to accommodate the consistent changes required by the astronomical calendar, so do not be alarmed when FOX Weather meteorologists say winter has finally begun on Dec. 1.
Meteorological winter runs from December 1 to February 28, which tends to be a better fit for the coldest time of the year than astronomical winter.