Extreme Temperature Diary- Friday June 25th, 2021/ Main Topic: The Advent Of Pacific Northwest Heatwave “Beta”

The main purpose of this ongoing blog will be to track planetary extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉

Main Topic: The Advent Of Pacific Northwest Heatwave “Beta”

Dear Diary. Perhaps one of the most anomalous events, if not the most above average temperature events during our lifetimes on the planet, is about to happen in the Pacific Northwest. This Heatwave “Beta” event is why I started the Extreme Temperature Diary in the first place.

To start, since Seattle remains one of the largest U.S. cities in which the populace has relatively few air conditioners, I’m deeply concerned about suffering that could lead to fatalities there. Should this start to happen Beta would become a CAT4 similar to that of the 1995 Chicago heatwave, which killed 739 people. On Saturday the system will become intense enough to immediately get a major CAT3 ranking and thus the designation of a Greek name for this year, Beta.

As of Friday morning National Weather Service Heat Warnings have been posted for most of the Pacific Northwest and watches, once again unfortunately, have been posted for much of California:

Across Northern California Beta will do more dirty work where Alpha left off before moderating last week.

Already many media outlets are writing forecast summaries concerning Beta. This one from Climate Central appeared in my in box this morning. (This contains resources that on camera meteorologists will be using to inform the public about the connection between Heatwave Beta and climate change.) :


Historic heat wave for the Pacific Northwest

JUN 25, 2021

Extreme and dangerous heat will overtake the Pacific Northwest this weekend and early next week.

Extreme and dangerous heat will overtake the Pacific Northwest this weekend and early next week. Locations in Oregon and Washington will challenge all-time record highs, with temperatures edging above 100° in Seattle, and likely over 105° in Portland. Interior locations east of the Cascade Mountains, like Spokane, will soar to near 110°.  In many cases, temperatures will be 25-30° above normal. See forecast highs from the NOAA/NWS National Digital Forecast Database.

Below are some resources to cover this historic heatwave

Current all-time records (via NOAA ACIS)

The Climate Connection

There is a strong and direct link between extreme heat and climate change. In a warming climate, extreme heat is happening more often and lasting longer. 

Quick points:

  • The weather pattern building into the Northwest is referred to as a heat dome and is associated with a blocking jetstream. The influence of climate change on blocking blocking weather patterns is an active area of research
  • Parts of the Pacific Northwest are locked in a severe to extreme drought. Dry soils heat more easily than moist soils, contributing to the higher temperatures near the ground. And as the climate warms, soils dry out more quickly, reinforcing the heat and making droughts worse


A small increase in average temperature leads to a large increase in extreme heat. Download the graphic at left.
A key indicator of a warming climate, the number of new record high temperatures is outpacing the number of record lows. Find graphics for all cities (i.e. Portland).
Our 2021 summer package contains city-specific data for the number of hot days, the average summer temperature (i.e. Seattle), and the average summer low temperatures.
The relationship between carbon dioxide and temperature is well defined. The increase is from the burning of fossil fuels, and the jump in each has been especially strong the past few decades.

Special Workshop

Watch our workshop on extreme heat from our recent Covering Disasters series: Extreme Heat 2020.


Extreme heat is the leading weather killer. This is especially true in climates that are not accustomed to it. 

  • 91 percent of American households have some type of air conditioning, the number is smaller in the Pacific Northwest — 44 percent in Seattle and 79 percent in Portland.
  • According to the CDC, an average of 702 heat-related deaths occurred in the United States annually between 2004-2018. And heat exposure and its impacts fall unequally, with historically underserved populations facing greater health threats. That disparity means that Black, Indigenous, Latinx, Asian, Pacific Islander, and multiracial populations, as well as those with lower incomes, are at heightened risk.

Experts Available for Interview

Additional resources


One item I have neglected linking Beta with clinate change is the unusual 500 millibar pattern around the Northern Hemisphere, or one example of Dr. Michael Mann’s weakened jet caused by warm pockets getting very far north, and this is what we see:

On the above chart blue cold pockets are swirling around in closed circles. Beta is building across the Pacific Northwest in red. Another heat wave is apparent in Russia. In prior decades cold blue areas would be further south and less numerous with one or two pockets covering more area across the Northern Hemisphere even during the summer.

Bob Henson has written an excellent summary involving records for the Pacific Northwest Area:


Northwest U.S., British Columbia brace for historic, record-melting heat

All-time record highs may be toppled in large cities and small towns alike

by BOB HENSON JUNE 24, 2021

People in park during heat wave

Seattle residents sought relief in green spaces during a fierce heat wave in the last week of July 2009, when the city saw its highest temperatures ever recorded. (Image credit: Michael B. / CC-BY-NC-ND 2.0)

A shockingly intense heat wave for the location, and for so early in the year, will produce some of the highest readings ever observed across much of the Northwest U.S. and adjacent southwest Canada. Temperatures will soar to dangerous levels – well above 100 degrees Fahrenheit in many places – from Friday, June 25, into the following week, in a region where hundreds of thousands of residents lack central air conditioning or any AC at all.

For several days, multiple computer forecast models have been spitting out astonishing numbers for Portland, Oregon; Seattle and Spokane, Washington; Vancouver, British Columbia; and other towns and cities. Even with some potential model overestimation, confidence is growing that a truly historic heat wave is on tap.

One sign of this is official forecasts from the National Weather Service: They’ve grown bolder through the week as model agreement has solidified and the event has drawn closer. As of midday Thursday, June 24, the National Weather Service forecast was calling for Spokane to hit 110°F on both Monday and Tuesday, June 28 and 29. These would break the city’s all-time high of 108°F from July 26, 1928, and August 4, 1961.

In Portland, Sunday is predicted by the National Weather Service to be the hottest day in city history. The forecast high of 109°F would topple the all-time record of 107°F set on July 30, 1965, as well as August 8 and 10, 1981. (See more on local records below.)

It’s extremely unusual for the National Weather Service to predict three or four days in advance that all-time records could be not only approached but exceeded. Such is the projected intensity of this heat wave and the resounding agreement among the world’s top forecast models.

In some cases, the highest single-day low temperatures ever recorded may be challenged as well. Warm nights only add to the danger of multi-day heat waves.

Temperatures will be 20 to 28 degrees Celsius (36 to 50 degrees Fahrenheit) above average at 5 p.m. PDT Sunday, June 28, 2021, over much of the Pacific Northwest coastal region, according to the 12Z Thursday, June 24, run of the GFS model. (Image credit: tropicaltidbits.com)

“This will be an *exceptionally dangerous* heatwave from a public health perspective, especially since this is a part of the country where structures are not designed to shed heat and where air conditioning is rare,” tweeted climate scientist Daniel Swain (@Weather_West). “Infrastructure/ power disruption is also possible.”

What’s even more astounding and concerning is the timing of this event, weeks earlier than anything comparable in the past. Heat waves tend to be more dangerous when they occur early in the summer, before people have had time to fully acclimate to high temperatures.

Seattle’s official definition of a heat wave is at least three consecutive days topping 90°F. Such a streak has never before occurred in June, when clouds and cool air more often enshroud the city, delaying summer warmth and producing what’s known locally as “June gloom.” However, the city’s first June heat wave on record is almost certain to unfold from Saturday to Monday, June 26-28, with predicted highs of 95°F, 99°F, and 99°F.

Extreme as they sound, these forecasts might need to be adjusted even higher. As of early Thursday, June 24, a consensus product of models used by the National Weather Service (the National Blend of Models) was giving Seattle a high of 101°F on Sunday and 104°F on Monday. In Portland, the blend was calling for a Sunday high of 111°F.

The heat will be no less impressive north of the U.S.-Canada border. Temperatures in Vancouver, British Columbia, could reach 31°C (88°F) in town by Tuesday, June 29, according to Environment Canada. Readings at or above 37°C (99°F) are possible on the warmer east side of the metro area. Vancouver’s all-time high is 34.4°C (93.9°F). According to international weather records researcher Maximiliano Herrera, 36.0°C (96.8°F) was recorded at the West Vancouver station.

Farther east in British Columbia, the interior city of Kamloops is predicted to hit 40-41°C (104-106°F) on each day from Sunday through at least Wednesday. The city’s all-time high is 41.7°C (107.1°F), and the all-time record for Canada is 44.4°C (112°F), set at several locations.

The regional heat wave should abate in cities near the coast starting on Tuesday, but temperatures will remain mostly above average throughout the week. Meanwhile, the core of the heat will move eastward into Idaho and western Montana, possibly leading to all-time highs in that region as well.

What’s driving the heat wave?

As with most large-scale heat waves, the culprit in this case is an exceptionally strong upper-level high predicted to develop across the region. The high is partially a result of a pocket of rich moisture in the Northwest Pacific, with reverberations translating eastward along the jet stream and forcing the unusually strong upper high to develop, according to meteorologist Philippe Papin.

Another factor is the unusually parched landscape of eastern Washington, Oregon, and British Columbia. The dryness will allow energy from intense sunlight to bake the ground rather than evaporating ground moisture. Since March 1, Spokane has received just 1.10 inches of rain – the least moisture for any spring and summer to date since 1924. Every other such period in the last century has seen at least twice as much rain in Spokane. Wheat farms across eastern Washington, most of which lack irrigation, are suffering in the drought.

By one common measure, the heat dome at the center of this upper-level high will be as strong as any ever observed in the Pacific Northwest, if not stronger (see embedded tweet below). As warm air expands at lower levels, it pushes up the height of the 500-millibar surface, roughly at the midpoint of the atmosphere vertically. The 500-mb height is predicted by the European and GFS ensemble model averages to exceed 594 decameters from Washington state northward into Canada. The record-high 500- millibar height at Quillayute, Washington, as measured in twice-daily weather-balloon launches (soundings) since 1948, is 597 dm; no event before mid-July has seen anything higher than 593 dm.

You can read much more of Bob’s article by clicking on the following link:

I’ll be adding more information and record stats to the Extreme Temperature Diary as we move through the weekend.

Here is more climate and weather news from Thursday:

(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)

Now here are some of today’s articles and notes on the horrid COVID-19 pandemic:

(If you like these posts and my work please contribute via the PayPal widget, which has recently been added to this site. Thanks in advance for any support.) 

Guy Walton “The Climate Guy”

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