Published: August 2,2017
Early Wednesday morning, the sun set briefly in Barrow, Alaska – something that hadn't occurred there in nearly three months.
At 1:57 a.m. AKDT Wednesday, America's northernmost city saw a sunset for the first time since May 10, ending an 84-day period during which areas north of the Arctic Circle never saw the sun dip below the horizon.
During the Northern Hemisphere's spring and summer, the sun's most direct rays shine over areas between the equator and Tropic of Cancer, about 23.5 degrees north latitude.
Because the Northern Hemisphere tilts toward the sun in the spring and summer, areas north of the Arctic Circle – within 23.5 degrees of the North Pole – experience more than two months when the sun never dips below the horizon, evoking the popular phrase "Land of the Midnight Sun."
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Despite all this possible sunshine, average highs in Barrow – now known as Utqiaġvik – reach a yearly peak of only 47 degrees in July, thanks not only to the northern latitude, but also its proximity to the Arctic Ocean, which is covered in ice near the coast for much of the year. Barrow experiences 187 cloudy days a year because of dominant east winds off the ocean, according to data from NOAA's National Centers for Environmental Information.
From mid-November through late January, the sun doesn't rise north of the Arctic Circle, due to the tilt of the Earth away from the sun's most direct radiation.The opposite occurs from mid-November through late January, when the sun doesn't rise for about two months north of the Arctic Circle. In Barrow, this "polar night" will begin with the last sunset Nov. 18 at 1:38 p.m. AKST and continue until the sun pops above the horizon Jan. 22 at 1:26 p.m. AKST.
It's a common misconception that Barrow and areas north of the Arctic Circle are completely dark during this period.
Civil twilight, defined as the point when the sun is 6 degrees below the horizon, allows sufficient light to see objects outside. This civil twilight period is about 6 hours long near the beginning and end of polar night but shrinks to about three hours in the heart of the polar night just before Christmas.
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Fairbanks, just south of the Arctic Circle, still sees sunrise and sunset year-round. By the summer solstice around June 20-21, sunrise is as early as 2:59 a.m. AKDT, a little over 2 hours after sunset at 12:47 a.m. AKDT.
From May 16 to July 27, Fairbanks sees civil twilight 24 hours a day.
Brian Donegan is a meteorologist at weather.com. Follow him on Facebook and Twitter.
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