November 06, 2023

The Most Beautiful Weather Imagery Imaginable: Steam Fog over Lake Washington

 Last week a student in my Atmospheric Sciences 101 class, a member of the UW Crew Team (Marc Tennesen), showed me some pictures of steam fog taken early last week over Lake Washington.

I was stunned by their beauty and I want to share them with you.   Surreal, magical, ethereal.  Here are a few.

This is steam fog season around Lake Washington.  

Steam fog generally occurs when the air temperature is at least 20F cooler than the water temperature.  Such a condition is most frequent in fall when the water is relatively warm after a summer of sunshine.

Below is a plot of Lake Washington's water temperature this year.  Got as high as roughly 70F in late August, and was about 55F early last week.   Early last week, surface air temperatures dropped down to freezing, providing a large temperature differential between cool air and warm water.  Thus, the steam fog.

The warm water warms and moistens the air near the surface.  Mixing in some cold air, results in the mixture being saturated--100% relative humidity--thus allowing the formation of fog.


  1. It's a fascinating phenomenon. Great photos, too. Thanks.

  2. are they all rowing frantically in order to escape Seattle?

  3. Interesting, isn't it, how they admonish us kayakers to wear lifejackets all the time and, like cattle, most follow the lead. But rowers? They don't wear them. Doesn't make sense to me, especially since those rowing shells have only about 6 inches of freeboard.

    1. Your comment assumes that crew coaches understand the basics of hypothermia and thus make informed decisions. Mario Vittone, former USCG helicopter rescue swimmer and hypothermia expert, has lambasted crew coaches for how they conduct basic marine safety.

  4. Do you have temp data for Puget Sound? Assuming the thermal cycle is much smaller than Lake Washington...

  5. Unfortunately for us swimmers, Puget Sound rarely tops 55 degrees F., except in protected bays on a rising tide when the sun has heated the mud flats. But due to the sound's depth and substantial tidal exchange, the open water generally stays in the mid-fifties. I measured 51 in August once off Port Townsend.

    However, Hood Canal is an exception. Much of it reaches 70 degrees or a bit higher in July and August. I have measured it myself.

  6. Steam rising over eastern Washington State

    I love the smell of nuclear fission in the morning. It smells like .... victory.

  7. Thank you for sharing something beautiful!

  8. I would be proud to display those photos on my living room wall!...So essentially Seattle!...thanks so much!

  9. Fun stuff!, Check out my video on the steam fog over the Puget sound around the same time.


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