Why are Western WA mornings still so foggy in the summer?
Jun 23, 2024, 10:09 AM | Updated: Jun 24, 2024, 5:47 am
Early morning fog in Seattle before sun breaks, turning into a typical summer day. (Photo courtesy of KIRO 7)
(Photo courtesy of KIRO 7)
Someone in Western Washington woke up this morning, looked out the window and voiced, “Where’s the sun? I thought summer was here!”
Welcome to the marine layer. A listener recently asked what is meant by the marine layer. You’ve likely heard television weather anchors and others use the term, so what does that term mean?
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The month of June often involves low-level onshore flow from the Pacific Ocean that creates marine low cloudiness in the mornings. With the sun so high in the sky around the time of the summer solstice and into summer, the marine clouds often give way to afternoon sunshine and mild temperatures. Think of the onshore flow from the Pacific as nature’s air conditioning.
The tops of those marine clouds help define the height of the marine layer. Have you taken a flight out of Seattle-Tacoma International Airport (SEA), Paine Field or another local airport with marine clouds in place and, not long after takeoff, you climb above the marine layer into brilliant sunshine?
The tops of the marine layer can vary. Often, it is around 2,000-3,000 feet, but can be as low as 1,000 feet or less, or above 4,000 feet, usually meaning it will take longer to give way to afternoon sunshine. Sometimes the marine layer will also squeeze out a little drizzle or mist.
Temperatures above the marine layer are commonly warmer than below – a temperature inversion. With the high-angle sun, that temperature inversion breaks down as the air near the ground warms up, dissipating the clouds.
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Visible satellite imagery can show the marine clouds that tend to bank up along the Cascades and Olympics. Visit Zoom Earth online for those days with marine clouds, and put it in loop or play mode to watch how it erodes as the afternoon approaches.
I hope that answers the question about what is meant by the marine layer. If you have a Western Washington weather question, send it along to feedback@mynorthwest.com and your question may be in a future story.
Ted Buehner is the KIRO Newsradio meteorologist. You can read more of Ted’s stories here and follow him on X, formerly known as Twitter.
