December 21 this year marks the winter solstice (a.k.a. “first day of Winter”, “shortest day of the year”, etc.) in the northern hemisphere. Because our planet Earth is tilted on its axis, the angle of the sun’s rays varies throughout the year, hence, the changing seasons! Here’s more from AccuWeather!
So, just because after today, the days begin to get longer, don’t get your hopes up. As the old saw goes, “The New Year now begun, as the days began to lengthen, so the cold began to strengthen.”