Actually only because of our Axis's Tilt of
≈5° 23.43643° [corrected] which favors the Northern Hemisphere.
Note: Solar Energy Angle of incident is ≈5°
No Winters when Dinosaur's walked the Earth.
Just the beginning of the Polar Jet Stream dipping down south, thus the COLD begins.
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"Winter in the Northern Hemisphere will officially commence on Tuesday, December 21 at 15:59 UT (or 10:59 a.m. EST and 7:59 a.m. PST). At that time the sun will reach the solstice - its southernmost declination for the year, resulting in the lowest noonday sun, the shortest amount of daylight of the year for the Northern Hemisphere, and the longest amount for the Southern Hemisphere. After the December solstice, the daylight hours will begin to increase for the Northern Hemisphere"
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By the way..
Did you know a rare event will occur on Xmas night?
Christmas Star
Check out the news.
Jim...
PS: Thanks for the correction
@Johnb