While December signals the start of meteorological winter, the Northern Hemisphere technically remains in astronomical autumn for a few weeks more. The difference between the two comes from how seasons are defined. Astronomical seasons depend on where the Earth is in its orbit around the sun, with significant events such as the winter solstice signaling the start of winter.
When is the Winter Solstice?
One of the most significant astronomical events is the winter solstice, when the North Pole is tilted as far away from the sun as it possibly can be. This usually translates into the shortest daylight time of the year in the Northern Hemisphere and tends to have the coldest temperatures of the season. The National Weather Service has reported that the solstice will occur this year at 3:21 a.m. Central Standard Time on Saturday, December 21.
What About the Shortest Day of the Year?
The shortest day of the year occurs during the winter solstice, but the shortening daylight that leads up to the solstice starts a little earlier. This Monday in Chicago, sunsets start earliest at around 4:19 p.m. They’ll continue that way until December 14 when sunset time shifts to 4:20 p.m. Although the sunset time will remain constant, the sunrise will continue to occur later every morning, reducing the daylight hours by about one minute every day. By December 21, the shortest day in Chicago will have only nine hours, seven minutes, and 44 seconds of daylight.
When Will Daylight Start to Increase?
Starting the day after the winter solstice, daylight hours in Chicago will start growing, though it will be a very slow process at first. According to TimeandDate.com, in the last 10 days of December, daylight will increase by only about four minutes, with sunset pushing to just before 4:30 p.m. The shift will linger into the new year and will be the latest on which the sun rises on the day around 7:18 a.m. during each day of the month. By late January, the city will see daylight increase for two minutes every day, when sunset passes 5 p.m. for the first time since daylight saving time ended on November 3. On January 30, Chicago will cross the 10-hour mark for daylight, with longer days to follow as winter progresses.
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