Tomorrow is the first day of (astronomical) winter! You may remember we also ushered in the cold season on December 1, so let's discuss the difference. 

In the weather community, we keep records based on seasons. These records are how we tell you we are close to having our driest summer or hottest spring on record, for example. Meteorological winter, for record-keeping purposes, starts on December 1. That's an easy thing to mark on a calendar and signals the time of year when temperatures start to drop to their coldest. 

The seasons we experience are actually dictated by our place in the universe which is why astronomical winter starts tomorrow. December 21 is the winter solstice, the day we experience the least daylight. Louisville only gets nine and a half hours of daylight. This happens because the earth is titled on its axis, and tomorrow's winter solstice marks the point at which the north pole is farthest from the sun. In the image above from NASA, you can see in December the north pole is tilted away from the sun which brings us cooler weather and less daylight. So happy Winter Solstice/Astronomical Winter!