May 07, 2023

How Does the Strengthening El Nino Influence Summer Weather in the Northwest?

NOTE:  Last Day to Register for the NW Weather Workshop (see bottom of blog for information.


I have gotten a number of emails wondering about the impacts of the developing El Nino on our summer weather.  

And several media outlets have already suggested that El Nino will cause enhanced heatwaves around the folks are a bit worried (some samples below)

The Bottom Line:    The correlation of El Nino (warmer than normal water in the central and eastern tropical Pacific) on Northwest summers is quite weak.   The El Nino signal tends to increase after January 1.

NOAA provides a number of graphics and studies that have taken on this question.

For example,  below is the correlation between summer (July-August temperatures) and the temperature in the central/eastern tropical Pacific (the Nino3.4 area).   A positive value would be consistent with El Nino causing the summer temperatures to warm.

Interestingly enough, El Nino results in COOLING over most of the U.S..    But western Washington and Oregon are the stand-outs, with a modest positive correlation of about 0.4.  This means about 16% of the variability of summer temperature in our area might be explained by warmer tropical sea surface temperatures.

And western Washington and Oregon tend to be a bit warmer during El Nino summers. 

But you probably don't want to know about correlations, but how much warmer it might be.  

Below is the answer for the area around western Washington for June-July-August.  It suggests that the median temperature (the red lines) is about 0.5 degrees F warmer during El Nino summers than neutral (normal) summers.    Not much.

Perhaps a better map shows the summer (May through September) temperature anomaly from normal for El Nino years (below).  Near normal (within .5 degrees of typical) over the Northwest and cooler than normal over the Southwest, and the high plains.

What about summer precipitation during El Nino years?  As shown below, near normal precipitation over the western U.S., slightly wetter than normal in the central U.S., but a bit drier than normal over the Northeast.

I would show you more graphics, but the answers are consistent.   The El Nino influence on weather is very weak or non-existent over the Pacific Northwest over summer and thus provides meteorologists no useful prediction signal during our warm season.

Sorry....wish I could say more!

Consistent with the above, the latest European Center model seasonal forecast predicts near-normal precipitation over the Northwest during June/July/August.

For temperature, conditions are predicted to be near normal over Washington, Oregon, and California but warmer than normal over southwest Canada.

A prediction of near-normal conditions will probably not secure much attention from the media.  Can you imagine this?


The Northwest Weather Workshop agenda and information are online.   This meeting, which will take place on May 12-13th in Seattle, is the major weather meeting of the year in the Northwest.   We have a varied and interesting agenda.  The meeting is open to everyone and if you want to attend you must register (on the website).   

We will also have a banquet/talk at Ivar's Salmon House on Friday May, 12.  This is a fun meeting and will be hybrid (in person and on zoom).


  1. Cliff, if weather forecasts for later this week and weekend are correct, then watch for a deluge of Climate Alarmism a la El Nino to ramp up exponentially. Like the swallows returning to Capistrano...

  2. The 2015 developing El nino summer wasn't a bit above normal it was well above normal, June through August had 12 90+ days and 51 80+ days for seatac. I'm not saying that's gonna happen every El nino is different ofcourse.

  3. But what about El NiƱo's impact on the International Moose Count?

  4. The moose count article is gold. Canada moose numbers to reach one million billion hahaha

    1. The moose article was riveting. So many things never covered in Seattle media. The Mongolian moose trade imbalance is concerning. The loss of the Singaporean moose cargos was tragic. But the biggest tragedy was that the article was continued on the second page, but only the first page was published.

  5. (Good one, Micah! And, that's one heck of a "moose tail" Prof.)

    That said, it was interesting to see the graphic that compares the effects of the Three N's (Nino, Neutral, Nina). The differences are not massive, nor cataclysmic.

    I find most "Seattle weather stories" that navel-gaze SeaTac (airport) statistics in the range of "curious-to-amusing." The numbers may be real; and better than they used to be (I understand there have been calibration problems, challenges). The are (how many?) acres of runways plus buildings (w HVAC) and warehouses; cars, busses, pavement; and masses of air pass through hot jet engines, plus prop wash and uuuge wakes as planes take-off and land. Pilots do need to know what's going on, what conditions are - absolutely. But I don't see that there's a lot about the "weather station data" at SeaTac that relates directly (or correlates well) to big-W weather (regional fronts, polar-this, ocean-that). Is it not in a rain shadow? A person could devote an entire post to the microclimate. Maybe that's been done.

  6. Retrospective on the heat experienced in the summer of '21:

  7. The past 10 years of data for BLI appear to indicate that mean monthly temps for June-August will be above normal regardless of ENSO phase. Since 2013, every June except for that of 2020 has had an above normal mean temp as have 8 of the 10 Julys, excepting those of 2017 and 2020, as well as 9 of the 10 Augusts during that period excepting only that of 2020.

    For reference, using the Oceanic Nino Index (ONI), the summers of 2013, 2014, 2017 and 2018 were solidly ENSO neutral, those of 2016, 2020 and 2021 started ENSO neutral and graded into ENSO negative (La Nina), that of 2019 started ENSO positive (El Nino) and graded into ENSO neutral, that of 2022 was ENSO negative and that of 2015 was ENSO positive.

    From what I can tell, it also appears as though the summer of 2022 may be the first ENSO negative summer in BLI history during which all 3 summer months had above normal temps.

  8. Looks like China is catching up in moose exports, too! Wait till they start launching them from their new aircraft carriers and hypersonic missiles! Taiwan will be smashed!

    1. Chinese Moose infrastructure is very strong.

  9. I remember from my days in grade school in the late 1950's hearing about the International Geophysical Year, the IGY.

    The IGY was an international scientific project which lasted from July 1st, 1957, to December 31st, 1958. It marked the end of a long period during the Cold War when scientific interchange between East and West had been seriously interrupted.

    The IGY encompassed eleven earth sciences: aurora and airglow, cosmic rays, geomagnetism, gravity, ionospheric physics, longitude and latitude determinations (precision mapping), meteorology, oceanography, seismology, and solar activity. The timing of the IGY was particularly suited for studying some of these phenomena, since it covered the peak of solar cycle 19.

    Another momentous year for academia -- the Intersectional Metaphysical Year, the IMY -- is now in the works. The IMY is due to begin on July 1st, 2023, and to end on December 31st, 2024.

    As opposed to 1957's IGY, which was focused on real science, the IMY will be a pseudo-scientific exploration of all facets of alleged racism, alleged denialism, alleged genderism, alleged misogynism, and alleged facism -- in other words, any kind of alleged '-ism' you can possibly think of -- as is allegedly being perpetrated by one group against another, or by individual persons against other individuals of a different race, gender, creed, sexual orientation, economic class, education, and/or political philosophy.

    The oncoming Intersectional Metaphysical Year will be characterized by activities on campus and elsewhere in the real world not unlike those seen during Mao's 1967 Cultural Revolution. When it's all over, everyone involved will be suffering from a very large headache.

    And while the IMY is in progress, the earth's climate system will be warming from some combination of natural and anthropogenic causes, continuing to do so long after the Intersectional Metaphysical Year is a mere footnote in the history books.


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