June 02, 2023

Was May the Warmest in Northwest History?

During mid-May, when western Oregon and Washington were in the throes of a several day heat wave, while smoke from Alberta fires was moving in overhead, there was considerable talk about May being the warmest in the historical record for the region.

Was it a record?  Is May getting warmer in the Pacific Northwest?  Is global warming influencing May temperatures?

This will be the topic of this blog.

To begin, consider the difference (anomaly) from normal for the last 30 days for the average maximum temperatures (below).    Much warmer than normal for the northern tier of states, including Washington (as much as 6-10F in locations), but MUCH colder than normal in California and the Southwest.  

Folks I know in southern California have complained vehemently about unusual cold and wet conditions during May.


May in western Washington

    Let me begin by showing you the long-term temperature statistics for Olympia, Washington.  

Why not SeaTac?  

Because of the addition of a third runway and the substantial urbanization and development around SeaTac, its observations are NOT reliable for climate studies.  Far fewer changes and a more rural character for the area around Olympic.

First, consider the mean maximum for May at Olympia, going back to the early 1940s.  May 2023 was the third warmest on record.   But also note that May 2022 was one of the coldest and that there is no long-term trend for high temperatures at Olympia, suggesting climate change is small for that parameter.


What about the highest temperature observed in May for Olympia (see below)?  May 2023 was warm but a number of months were nearly as warm.  Importantly, there is no upward trend of extreme high temperatures in Olympia.


But the story is different for average May minimum temperature at Olympia, which has risen from roughly 41F to 43F.   

It is well known that increasing greenhouse cases have more influence on daily low temperatures than high temperatures.  Furthermore, local development (and there have been some near Olympia Airport) influence low temperatures more than highs.


May in eastern Washington

    Let's review the temperature in Kennewick, Washington in the Tri-Cities.  This station has a very long record (back to the 1890s) and far less localized development (below). 

May 2023 had warm high temperatures, which were exceeded several times druing the 1920s-1950s.  Note there is a DOWNWARD trend in the high temperatures at Kennewick.  I repeat: downward.

This plot is also a good illustration of why long records are important.  A record going back only the 1970s would suggest 2023 was the warmest ever observed, inspiring all kinds of headlines in local newspapers.  But a longer record, such as at Kennewick, shows that such temperatures were frequently observed in the past and that the long-term trend is downward.


The extreme monthly high temperatures in May for Kinnewick are DECLINING and 2023 was nothing special (below).


In contrast, the mean minimum temperature has risen by approximately 2F during the past century at Kennewick, with 2023 being the second warmest on record.


The Bottom Line

    May high temperatures on both sides of the Cascades were warm, but not record-breaking.  Importantly, there is no upward trend of the high temperatures on both sides of the Cascades, suggesting that global warming/climate change is having relatively little impact on the region's high temperatures.

In contrast, low temperatures have warmed modestly (roughly 2F) during the past century and part of that might well be due to anthropogenic warming resulting from increasing greenhouse gases (most importantly CO2 and methane) and increasing urbanization and development in the vicinity of temperature sensors.  Low temperatures are also more sensitive to wind anomalies from normal.  For example, May 2023 had far more easterly (from the east) winds, which tend to cause minimum temperatures to warm.


27 comments:

  1. Interesting. In B.C., there were numerous sites that recorded their warmest May on record this year. Environment Canada tweeted out a partial list that included 16 locations that broke the record. Victoria (Gonzales) broke its record, with data collection going back to 1899.

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    1. I just checked... Victoria Gonzales did NOT achieve their record May temperature...cliff

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    2. Cliif's analysis of May temperatures at Olympia and Kennewick pretty much matches that at the Tree Fruit Research Center in Wenatchee, whose temperature record goes back to 1940 with mean values computed for the period 1940 to1993. Compared to those long term mean values, the average maximum temperature for the 24 Mays since 2000 is very close to the long term average, but the average May minimum temperature since 2000 is about 2.6 degrees above the long term average.
      The summer average minimum temperature (June thru August) since 2000 thru 2022 is about 3.8 degrees above the long term average with only 3 summer months in this century recording a below average minimum temperature. The TFRC weather site is in a semi-orchard environment with little change in the surrounding area over this period of record so one would have to believe it is due mainly to the warming climate.

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    3. I'm not sure where you saw that. Victoria Gonzales had a mean temp of 14.3 C in May. The old record was 14.2 C in May 2005. Environment Canada confirmed this.

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    4. just checked the data again. 2023 was not the warmest
      1 2014 58.0 18
      2 2019 57.8 16
      - 2016 57.8 16
      4 2023 57.6 19

      Also checked nearby discovery island. Not urbanization issues. 2023 was not the record.

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  2. If you look at the WA statewide annual minimum temperature data, there was a bit over a 2F increase between 1874 and 2022, but 2F of that increase was between 1970 and 2022, a period of 50 years, not a 100 years.

    https://public.tableau.com/shared/WFTSH29KT?:display_count=y&:origin=viz_share_link&:embed=y

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    1. You are not correct. Although the majority of the warming occurred after1970, there was notable warming from 1896 to 1970. I am referring to the NOAA division data set for Washington.

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  3. Hey Cliff, can you elaborate why it is important that high temperatures show no warming trend? I think it would be equally important to highlight the increase in the average temperature in your summary.

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    1. There are two reasons. First, high temperatures during the warm season are generally what stress people (heatwaves). Second, the difference between the trends of high and low temperatures (I showed both) are important. Remember, the average temperature is the average of the highs and lows and thus provide far less information and insight that looking at the separately. Hope this helps..cliff

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  4. ..."might well be due to anthropogenic warming resulting from increasing greenhouse gases (most importantly CO2 and methane) and increasing urbanization and development in the vicinity of temperature sensors."

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  5. Odd think about Olympia is that it often has the most extreme temperatures in Western Washington, particularly low temps in winter.

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    1. not odd at all. Olympia has more extreme temperatures because it is away from the water and h as a more continental climate. Also less urbanization. But the nature of its climate is not the issue. It is about sensing long-term temperature trends...that is the point I am making. If this is not clear to you, let me know and I will explain in more depth.

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    2. I am confused. I assume when you mention Olympia, you are speaking of the Olympia Regional Airport, which is not in Olympia but south of Tumwater. Olympia itself is on the water--the southernmost end of the Puget Sound. I agree its weather is more extreme. When mentioning Seattle temperatures, you are referring to Sea-Tac, not the city of Seattle, correct?

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  6. I had noticed for many years living in Chehalis, even further from the water, that Olympia often had winter temperatures below Chehalis.

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  7. I thought this spring was rather cold, with the exception of maybe a couple of days of 80+ temperatures mud May.

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  8. Hi Cliff have you ever researched Grand Solar Minimum cycles? We're entering one now and it will throw a bunch of curve balls in the climate system, nothing the mainstream media will cover

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  9. One thing that's true is that given how dry the water year and calendar year have thus far been, along with the rapidly increasing evapotranspiration to precipitation ratio, and given the lack of substantial precipitation in the forecast, vegetation is going to start drying out markedly over the next couple of weeks and you can be certain that by Independence Day fire danger will be very high. This is going to be yet another smoky summer.

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    1. Friend: You can not assume the past is a good forecast for the future. In fact, we have a cooler/wetter than normal period ahead. You can not assume a dry May means more wildfires. You are posting message after message with your fears of disaster. The planet is warming slowly but most extremes are due to natural variability.

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    2. Over the years I've been continually amazed at Cliff's restraint at dealing with the Climate Cultists who come on here and refuse to acknowledge their ignorance and misstatements of fact on this issue. H.L. Mencken once said that no one ever went broke underestimating the intelligence of the American public, and even though that comment was over one hundered years ago, that truth has even more validity today. We have easy access to information that was undreamed of less than twenty years ago, yet some of us are more ignorant than ever before.

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    3. Lets hope Cliff's cool, wetter than normal weather arrives and is more prolonged than in recent summers. We have had a dry, warm several weeks here in central Washington, the snow left earlier than normal and the grasses are already curing. With the high sun angle and warm dry weather over the next several days, we could get into an early fire situation. And we would need more than just a few showers and brief cool weather to overcome this, especially if the rest of the summer is warm and dry as predicted .

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    4. Something I find weird is how often Cliff plainly states that warming is happening and is partially due to greenhouse gas emissions, yet the "skeptics" on this blog can't even live with this very modest and conservative view. Pushing back against ostensible climate sensationalism and alarmism with equally absurd denial isn't helpful or productive.

      One other thing, where is this cool/wet period you're seeing, Cliff? Looking at various 10 day forecasts shows mostly clear days and even a high of 85 midweek. This doesn't seem to indicate a pattern shift to cooler/wetter conditions in the near future.

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    5. S Young...just be patient for the end of the week....

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    6. I'd certainly bet on smoke this summer. Regardless of what you think is causing it, we've had so many smoky summers over the last 5-6 years that it's pretty hard to believe it's just a fluke at this point. As with most of these things, I hope I'm wrong... the smoke tends to ruin hiking season.

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  10. Fires need a source of ignition. About 84% are caused by something humans have done or do. WA fire folks caught on a few years ago and are doing a better, than it the past, job of (1) education, (2) fire-wiseing places, and (3) quickly getting to ignition points, thus keeping firs small. Applause, please.
    I have Ponderosa Pines – a fire wise tree - on my small patch of Earth and have seen serious fires from my driveway; Snag Canyon and Taylor Bridge to name two.

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  11. This is very strange. This map from the NOAA Climate Prediction Center has Thurston County shoved way south from the Puget Sound with Pierce County continuing all the way to Mason County. Looking at this map you might think Olympia was located away from the water. Why would NOAA misplace Thurston County? https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_monitoring/CLIM_DIVS/washington.gif

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  12. Hi Cliff. Speaking of Olympia it is dry as bleep down here already. Any rain before October in the forecast?

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Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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