Sunrises, Sunsets and Solstices
We all know the shortest day of the year is the winter solstice. The 2022 winter solstice will fall on December 21, and Seattle will only receive only receives 8 hours, 25 minutes, and 25 seconds of daylight during that day. At least there are plenty of holiday lights to keep things bright after the sun goes down.
But surprisingly, the winter solstice does not feature the earliest sunset or the latest sunrise of the year. The earliest sunset this year will occur on December 9, when the sun sets at 4:19 pm, while the latest sunrise will occur on January 1 at 7:55 am. Compare these times to a sunrise/sunset split of 7:52 am and 4:22 pm on December 21.
Why don’t the latest sunrise and earliest sunset fall on the winter solstice? The answer is because “solar noon,” the time at which the sun is at its highest point in the sky and is perfectly midway between sunrise and sunset, is trending later and later over the month of December. Without getting too technical, solar noon changes throughout the year for two reasons; first, the Earth orbits around the sun in the ellipse, not a perfect circle, and orbits fastest when it is closest to the sun, and second, the Earth is tilted on it’s axis relative to it’s orbital plane, causing the sun to appear higher or lower in the sky based on the season. Both effects combine to create the “equation of time,” which tells us the timing of solar noon throughout the year.
So even though the solstice will occur on December 21, we can look forward to our evenings getting a tad lighter after December 9 due to solar noon getting progressively later throughout December. And by next month’s Leschi News issue, both our sunrises and sunsets will be getting earlier and later, respectively, and we’ll slowly–but surely–climb our way out of the depths of winter and into early spring.
Charlie Phillips is a Madrona native and lifelong weather geek who now works at Puget Sound Energy as an energy trader, making sure there is enough energy to keep the lights on! Check out his weather blog at weathertogether.net.