June 02, 2021

The Heat Wave Ends As Marine Air Starts Pushing Eastward

 The temperatures during the past month have been a roller coaster, with extended periods of above normal and below normal temperatures (see plot below for Sea-Tac, the purple line is the normal high, the cyan line is the normal low).  The last two days have topped out around 85F, around 20F above normal!

Did we break any temperature records during the period? 

Not one (see plot below, which show the observed highs and lows, with the dashed lines showing the daily records).    This time of the year you have to exceed 90F to have a chance of a daily high record, below 40F for a record low.

80s F were prevalent today over the Puget Sound interior and low one hundreds in the Columbia Basin (see today's highs in the graphic below, click on image to enlarge).

An upper-level trough of low pressure is approaching as I write this blog, and this feature has initiated an onshore push of marine air.   Our natural air conditioner. 

 One sign of the push is the winds at Shelton--located to the northwest of Olympia and an excellent location to look for marine air surging from the coast to the southern Sound.  The winds at this site started to increase rapidly from the southwest (see below) this afternoon,  gusting to 25 mph, a sign of the influx of cooler, ocean air.

Shelton Wind Speed

Another sign of the push is that the pressure difference between the western Washington and coastal zone has increased considerably, with higher pressure along the coast.   Expect partly cloudy skies and highs around 70F tomorrow.  My dog will be happier.

But the big shocker will the rain on Saturday, which will be enough to be significant (see 24 h totals). Very needed and welcome after a dry spring.  And even more on Monday.

Precipitation this time of the year is of great value.   It both lessens the water needed for irrigation and slows the drying in wildfire-prone areas.

Many are asking whether this will be a bad wildfire year in the Northwest.    I will take up that question up in a future blog.  But let me note that a repeat of the September western Oregon wildfire event is highly unlikely, since it was forced by record-breaking winds from the east.


  1. Here in the Columbia Gorge, we've had a cool spring, sometimes even cold, prior to this week. We grow a lot of vegetables, and the impact is plainly visible.

  2. Cliff, what do you think of this inaccuracy on the long term climate predication? https://www.space.com/satellites-underestimated-global-warming

  3. Hi Cliff - any guesses when the rain will hit Saturday?


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