June 01, 2018

Warmest May on Record for Seattle, Tied for Driest May

Weatherwise, we just went through what was probably the finest May at Seattle for the entire period of record (from 1894 to today).

The monthly average was 61F, beating out the 60.5 in 1940 (see below).     In precipitation, the monthly total was .12 inches tying the amount observed in 1992.

It was a real nail-biter yesterday around dinner time as a line of showers went through...fortunately, there was only a trace of rain...which doesn't count.

But there is more: the average temperature this May was higher than the normal average for June (59.5F), this has happened only once before.  And every day this May reached 60F, something that only happened once in the climatological record--in 1947.

Why such a nice month?  Because there was a persistent ridge of high pressure over and to the north of Washington.

To illustrate this, here is the difference from normal of the heights at the 500 hPa pressure level (around 18,000 ft).  The yellow blob north and east of western Washington shows a center of above-normal heights... known as a ridge of high pressure.  Such a ridge of high pressure is associated with warm, sinking air.

The weekend should be pretty normal-- middle to high 60s, considerable clouds, and a few sprinkles, through mid-day Sunday, followed by an increasing shower chance later in the day.


  1. I felt like a kid on the first day of summer vacation -- on every day this May. Warm, dry days and cool nights. My version of paradise.

    Of course, now I am completely and thoroughly ruined, my expectations lifted to ridiculous heights as we go into June. When one stands on the pinnacle, there is only down. But maybe we can cling to the summit for a few more days?

  2. Most likely, John, we start down and must cross a deep valley, filled with slide alder and devil's club, and wade several creeks. We will start ascending the next mountain in late June and summit around the end of July... Sometimes I think climate change in "improving" the situation, but Cliff doesn't think it will.

    Otherwise, go to Eastern Washington.

  3. Water temperature in the Columbia River at Bonneville is above the 10 year average by several degrees as well. Temperature data here as well as fish ladder counts by species.

  4. I have to be a contrarian. I know this kind of May weather is not normal and worry that it portends a summmer of drought. NOT what I've come to expect after living 35+ years in the Puget Sound area. If things get much above 70, I'm not a happy camper.

  5. This sounds familiar. Another year of record rains in the winter followed by a long, dry, hot spring and summer? Let's hope not.

  6. "...worry that it portends a summmer of drought. NOT what I've come to expect after living 35+ years in the Puget Sound area."

    This is exactly the kind of history revision re: climate - and particularly precip in our region - that needs to stop.

    How is a "summer of drought NOT" (your caps) what you've come to expect, since our climate has always had summers of drought. Always. http://cliffmass.blogspot.com/2013/07/secret-revealed-northwest-has-best.html -- "We have practically NO RAIN (Cliff's caps) in the summer. Really. Seattle is drier than Phoenix in July."

    Meaning it would be abnormal if it was wet - at all.

    Climate history revision is a big part of the problem these days. Seattle does not have wet summers - in fact it has very dry summers. It is why we have very large reservoirs. Climate history revision needs to stop.

  7. Unknown...... This May has been above Average but it appears to be within the Range of Normal temps. There is an important distinction between the terms 'Normal' and 'Average', semantics matter. I've lived here considerably longer than your mentioned time frame and my take is that this one is at the higher end of the Normal Range.

  8. Four of the last five years in the top ten for May temps. Nothing to see here...

  9. You people have to stop posting those pesky facts and figures, when the only thing that really counts are feelings and emotions. Won't you think of the children?

  10. Paul, I doubt you have lived here considerably longer than your mentioned time frame since 1894 to 2018 is 124 years.

    "Weatherwise, we just went through what was probably the finest May at Seattle for the entire period of record (from 1894 to today)."

  11. WQR-......read over. My statement was directed to Unknown's comment wherein his time of reference was only "35+ years".

  12. Paul - air temperatures were warm, but there was a *huge* snowmelt from Canada coming down the Columbia River in May.

    I think you are reading the water temperature graph wrong, that you linked to. The 'scrollcase' is a spot in the hydroelectric dam where they measure the temperature. The tailrace and forebay gauges are in different locations and depths. I think you would only want to compare the yellow dot (historical mean) with blue dots, but they aren't showing current scrollcase. The green dot gauge is in a different location.

    This also lets you visualize current and historical average, and it shows we are at or very slightly below average water temperature at Bonneville this year.

    Pick other locations and variables here: http://www.cbr.washington.edu/dart/query/river_graph_text


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