When is northern hemisphere’s earliest sunrise?
Los Cabos sunrise
(Credit: dro!d. Some rights reserved.)
Friday, June 13, 2008
The earliest sunrise of the year will come tomorrow for mid-northern latitudes – for example, New York City.
Meanwhile, tomorrow will be the earliest sunset of the year at middle latitudes south of the equator – like in Hastings, New Zealand. Many people notice that the earliest and latest sunrises and sunsets don’t exactly coincide with the solstices. They come a week or two before or after the solstice, with the exact dates varying according to latitude.
It happens because Earth’s orbit around the sun isn’t a perfect circle – and our cycle of day and night doesn’t jibe precisely with the relentless ticking of human clocks. So tomorrow may be your earliest sunrise – or earliest sunset. Just know that this event – earliest sunrise or sunset – is happening for you sometime around now. The sequence of these events is always the same. The year’s earliest sunrise always comes before the summer solstice.
And the year’s earliest sunset always comes before the winter solstice. Meanwhile, those winter and summer solstices always come on the same date, for Earth’s north and south hemispheres. In 2008, that date is June 20 according to clocks in the U.S.
In June and December – the solstice months – the Earth’s axis is most tilted relative to the sun. In both the northern and the southern hemispheres, the sun reaches its noontime position in the sky about one-quarter minute later daily by the clock. This discrepancy between solar noon and clock noon continues to accumulate. One week from now, the sun will reach its noontime spot about 2 minutes later on the solstice than it does today. The daylight hours between now and the solstice do not change substantially. But the later clock time for solar noon will also cause the sunrises and sunsets to come a bit later by the clock for the next few weeks.
At 40 degrees north latitude, the earliest sunrise of the year precedes the June summer solstice by about a week. Meanwhile, at 40 degrees south latitude, it’s the year’s earliest sunset that precedes the June winter solstice by one week. Two weeks from today, it’ll be the latest sunset at 40 degrees north latitude, and the latest sunrise at 40 degrees south latitude.
At latitudes closer to the equator, the earliest sunrise/sunset comes at an earlier date and the latest sunrise/sunset happens at a later date. At Honolulu, Hawaii, for instance, the year’s earliest sunset comes about 2 weeks before the June summer solstice and the year’s latest sunset occurs about 2 weeks after the June solstice.
As you get closer to the Arctic and Antarctic Circles, the dates for the earliest sunrise/sunset and the latest sunrise/sunset converge closer together. For instance, at Fairbanks, Alaska (just south of the Arctic Circle) the earliest sunrise and latest sunset pretty much happen on the day of the summer solstice.
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