The Chicago Tribune reports that winter solstice will occur at 11:30 pm CT Wednesday night. This will mark the beginning of winter and the shortest day of the year.
The winter solstice marks the Northern Hemisphere's shortest day of the year. Chicago will only see nine hours and seven minutes of daylight on Thursday. Compare this to the 15 hours and 13 minutes of daylight the city saw during the summer solstice.
The winter solstice marks the time of the year when the sun's most direct rays reach the farthest south on the planet. From this point on, the Northern Hemisphere will slowly gain more and more minutes and hours of daylight, culminating in the summer solstice.
Read more about the winter solstice here.