As the spring equinox approaches next week, I am reminded of some of the comments I have received regarding my living in Alaska, over the last couple years. Comments like, “Isn’t it dark up there for 6 months straight?”, and “It must be great having sunlight all the time in the summer!” Well, without going into a lecture on planetary orbits and the angle of the earth’s axis relative to the sun, here is a brief explanation of what really happens.
First of all, just like every other location on our planet away from the equator, the number of daylight and nighttime hours in Alaska varies day by day, over the course of the entire year. There are four key events throughout the year that we all have in common:
Spring Equinox: the day when we have nearly the same number of daylight hours as darkness (about 12 hours each), March 20, 2018
Summer Solstice: the longest day of the year, meaning the day in which we will see the most daylight hours, June 21, 2018
Fall Equinox: the day when we have nearly the same number of daylight hours as darkness (about 12 hours each), September 23, 2018
Winter Solstice: the shortest day of the year, meaning the day in which we will see the least daylight hours, December 21, 2018
Now, we all share a similar day on the equinoxes, but the kicker is the farther north you get, the greater the solstices are, meaning our longest day of the year is longer and our shortest day of the year is shorter. For example (for you fellow geeks out there) you can get an idea of where you lie in the grand scheme of things, by looking at the graph I attached.
Here in Sterling, Alaska we are at a latitude of 60.5 – so we are the purple line. I come from Western NY state, where the latitude is about 42.5 – so they are closer the medium blue line.
You will also note, that in transitioning from the equinox next week, to the summer solstice in June, we here in Alaska will be gaining daylight at a greater rate than other locations further south.
So where does this leave us? Here is a quick comparison:
Longest day has about 19 hours of daylight
Shortest day has about 5 hours of daylight
Average change in daylight per day: 4.6 mins
Longest day has about 15 hours of daylight
Shortest day has about 9 hours of daylight
Average change in daylight per day: 2.0 mins
One last comment, there are locations in the extreme north, in the arctic circle, some of which are in northern Alaska, that do experience days with no daylight, or no darkness. However, it is not 6 months long. For example, when the sun set in Barrow, AK on November 18, 2017, it did not rise again until January 22, 2018, 65 days later.
Regardless of where you are in the northern hemisphere, Happy Spring, and enjoy the lengthening days!