Autumn officially arrives at 4:18 PM CDT today. This day is called the autumnal equinox. Even though most people believe that the length of the days and nights are equal on the first day of autumn (length of daylight today is 12 hours and 6 minutes), this actually occurs a couple of days after it. This is due to the way sunlight is refracted in our atmosphere. Across southeast Minnesota, northeast Iowa, and western Wisconsin, this typically occurs around September 25th. We will continue to lose daylight through December 17th. From this date through Christmas, the length of the day will be just under 9 hours (8 hours and 55 minutes).