In the parts of Alaska above the Arctic Circle, it is dark 24 hours per day for about 67 days during winter. Conversely, it does not get dark for about 80 days during the summer in the same area, a phenomenon known as the "Midnight Sun."
Places in Alaska south of the Arctic Circle experience varying degrees of darkness throughout the year. For example, on the winter solstice, there are approximately 18 hours of darkness in Juneau, but there are more than 20 hours of darkness on the same day in Fairbanks. Throughout Alaska, the amount of dark hours decreases from winter solstice to its lowest point during the summer solstice.