It
is ridiculous, and that's why it's a definition that should be ignored, and one of the more accurate definitions uses instead.
quote:
Astronomically, it starts with the winter solstice, and ends with the spring equinox
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In meteorology, it is by convention counted instead as the whole months of December, January and February in the Northern Hemisphere.
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the winter solstice is traditionally considered as midwinter[citation needed], the winter season beginning 1 November on All Hallows or Samhain. Winter ends and spring begins on Imbolc or Candlemas, which is February 1 or 2.
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the three-month period associated with the coldest average temperatures typically begins somewhere in late November