SEATTLE — While we have enjoyed a mild winter in Western Washington, many days have been filled with clouds and fog.
The time from December through January is often known as “The Big Dark” in the Northwest, when the least amount of solar radiation is getting to us from the sun.
But beginning Thursday, we’re now leaving the three-month period we meteorologists also know as “solar winter.”
Just as the seasons are three months long, “solar winter” is the period centered around the winter solstice — or start of winter — during which the sun is at the lowest in the sky in the Northern Hemisphere.
On the first day of winter, on December 21, the sun is only at around 19 degrees above the horizon in Seattle.
Halfway up is 45 degrees and directly overhead is a 90-degree angle.
While the sun isn’t all that much higher on February 5, we have already added more than an hour of daylight from the start of winter and the sun now reaches a peak of 26 degrees above the horizon — the same maximum elevation on November 7 when we started “solar winter.” The start and end aren’t the exact same day of the month because some months have fewer than 31 days.
On the first day of summer, June 21, the sun will be around 66 degrees elevation above the horizon. High enough to get some serious rays! But since we are so far north in latitude, the sun is never close to being directly overhead, but only about two-thirds of the way up.
To get a perfectly-overhead 90 degree sun angle, one must be between 23.5 degrees north and 23.5 degrees south latitude.
In the United States, only Hawaii, Puerto Rico, the U.S. Virgin Islands, Guam, and American Samoa are close enough to the equator to get sunshine directly overhead at any point in the year.
On those specific days when the sun is directly overhead, vertical objects like poles won’t cast a shadow around them because the sunlight is coming directly from above!