Winter officially begins with the Winter Solstice on Saturday, December 21, 2019. This is the astronomical first day of winter in the Northern Hemisphere.
The winter solstice is the day with the fewest hours of sunlight in the whole year. In the Northern Hemisphere, it always occurs around December 21 or 22. (In the Southern Hemisphere, the winter solstice occurs around June 20 or 21.)
In 2019, the winter solstice arrives on Saturday, December 21, at 11:19 pm EST.
Learn more at: https://www.almanac.com/content/first-day-winter-winter-solstice