Extreme Temperature Diary- Friday September 10th, 2021/ Main Topic: Deeper Dive Into The Significance Of America’s Hottest Summer

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: Deeper Dive Into The Significance Of America’s Hottest Summer

Dear Diary. I saw this historic note from my daily New York Times briefing email this morning:

“The Civil War led to the emancipation of Black Americans and a sprawling program of domestic investment in railroads, colleges and more. World War II helped spark the creation of the modern middle class and cemented the so-called American Century. The Cold War caused its own investment boom, in the space program, computer technology and science education.”

I’m hoping and working toward an outcome for the Climate War, which I consider to be our fourth great struggle as a nation, such that our energy will be supplied from renewables, and other facets of our civilization will become sustainable over the coming decades and centuries. Being a member of Al Gore’s Climate Reality has led me to also have the view that such a transition will lead to a much more equitable society in which racial harmony is further strengthened after initial Civil War and 1960s Civil Rights developments. Fighting the Climate War should further develop tech to make all of our lives a little easier in the long run, as well.

The events of this summer across the United Stares should also spur us as Americans to fight the good fight concerning the Climate War. Some of the worst consequences of climate change this year were the western fires, heat waves and drought; Hurricane Ida striking New Orleans and Louisiana; and many episodes of Northeast flooding. All of these events were related to the United States having its hottest summer in recorded history. So what was the significance of this historically hot summer?

My friend Bob Henson wrote a great post for Yale Climate Connections on our hottest summer. This post should answer my rhetorical question of the significance of this torrid summer, putting the last nail in the coffin of any skeptics who would stand in the way of our gathering army for change to fight the Climate War:


Sunset clouds at Alamosa, CO
Post-sunset clouds are tinged with wildfire smoke at Alamosa, Colorado, on Monday, September 6. Summerlike heat continued past Labor Day, as Alamosa set consecutive record highs of 87°F on Tuesday and Wednesday, September 7 and 8. During 115 years of recordkeeping at the high-desert city, temperatures have never gotten any warmer than 87°F so late in the season. (Image credit: Bob Henson)

An 85-year-old record for summer heat set during the Dust Bowl has met its match. In 2021, the contiguous U.S. had its warmest meteorological summer (June-August) on record, according to NOAA’s National Centers for Environmental Information (NCEI). Records going back to 1895 show the 48-state summer average of 74.01°F in 2021 came in just ahead of the summer of 74.00°F recorded in 1936. The margin of 0.01°F is close enough to be considered a statistical tie.

The record is especially noteworthy because many dismissive of climate-change science have trumpeted the heat of the 1930s in their efforts to downplay the importance of recent human-caused climate change in the United States. Doubters have long cited the full-year national heat record of 1934 even after it was beaten out in 1988. Since then, six years in the contiguous U.S. have ended up even warmer than either 1934 or 1988.

Figure 1. Average temperatures for the 48 states of the contiguous U.S. for summer (June through August) in records extending from 1895 to 2021. U.S summers have warmed by about 1.5°F over the past 125 years. (Image credit: NOAA/NCEI)

The 1930s were a notoriously scorching decade when many states recorded all-time highs and dust storms ravaged the Great Plains. Multiple studies have found that the extreme U.S. heat of the 1930s was likely the result of naturally occurring drought apparently triggered by warm sea surface temperatures in the North Atlantic, with the resulting surface heat exacerbated by the bare, over-plowed soil of the Great Plains.

Land management practices have averted any recurrence of Dust Bowl conditions ­– perhaps with an assist from ever-more-dense plantings in the Corn Belt that have exerted a cooling and moistening effect on summers in that region. Yet we’ve now had a 48-state summer just as hot as 1936’s, and perhaps a shade hotter.

Figure 2. Rankings of summer 2021 temperature (June-August) in each state compared to the past 127 years of recordkeeping. (Image credit: NOAA/NCEI)

The core of this summer’s U.S. heat was located west of the Continental Divide and across the northern tier of states into New England. Five states had their hottest summer on record – California, Idaho, Nevada, Oregon, and Utah – and 22 other states had a top-ten-hottest summer.

Western Canada burns and deaths mount after world’s most extreme heat wave in modern history

Across the summer as a whole, the most relentless heat in the U.S. West was focused east of the coastal towns and cities, thus affecting only a minority of the region’s population. The horrific exception, of course, was the catastrophic heat wave that struck western Washington, Oregon, and British Columbia, pushing temperatures to a mind-boggling 108°F in Seattle and 116°F in Portland, both on June 28. Early estimates showed more than 600 “excess deaths” in Washington and Oregon and more than 400 in British Columbia; it will take months more to determine a more precise death toll.

Figure 3. Rankings of summer 2021 precipitation (June-August) in each state compared to the past 127 years of recordkeeping. (Image credit: NOAA/NCEI)

A fierce drought in the West gets nipped by a welcome monsoon, but dire long-term situation ahead  

Widespread drought across the western half of the contiguous U.S. was tempered in late summer by a strong North American Monsoon that brought drenching, much-needed rains to parts of the Southwest. Arizona ended up with its seventh wettest summer on record, and New Mexico and Utah both placed in the wettest fifth of all summers since 1895. Further east, Mississippi had its wettest summer on record, and 10 other states east of the Mississippi, plus Texas, had a top-10 wettest summer. The only two states to have a top-10 driest summer were Minnesota and Montana.

Despite the generous monsoon rains, a severe long-term water deficit remains across the Southwest – the result of a 22-year drought punctuated by only brief periods of relief. Rising temperatures associated with human-produced climate change have worsened the situation by increasing the rate of evaporation from the landscape, including mountain snowpack, a crucial source of water. In August, the federal government declared a water shortage at Lake Mead for the first time in the reservoir’s 80-plus year history. The declaration will reduce the amount of water available to users in several states.

As of September 9, Lake Mead’s level of 1067.77 feet remained more than 15 feet below levels observed on that date in 2019 and 2020.

Figure 4. The central and eastern portions of Lake Mead, upstream from Hoover Dam, as captured by Landsat imagery on August 7, 2000 (left), and August 9, 2021 (right). (Image credit: NASA Earth Observatory)

The summer of 2021 was dimmed by wildfire smoke that spread across vast swaths of the nation, extending into September in many areas. Wildfires were particularly intense in the record-heat areas of northeast California, eastern Oregon, and eastern Washington. The Dixie Fire, which was threatening Lassen Volcanic National Park on September 8, is already the second largest fire or fire complex in modern California records, affecting more than 927,000 acres and torching more than 1200 structures.

Perhaps surprisingly, as of September 9, the nation’s year-to-date fire coverage – 5,165,103 acres – is the fourth lowest in the 11 years since 2011, according to the National Interagency Fire Center.

Figure 5. Rankings of summer 2021 temperature (June-August) in each U.S. county for average daily minimums (left) and average daily maximums (right) compared to the past 127 years of recordkeeping. (Image credit: NOAA/NCEI)

Wet conditions that prevailed across the South kept nighttime lows unusually warm but daytime highs cooler than average in most areas. Average daily highs were among the coolest third on record from Oklahoma and Texas east to South Carolina, but in the hottest third on record across the West, Northern Plains, and Upper Midwest, and from the mid-Atlantic to New England.

Average daily lows were in the top fifth of all summers on record for every contiguous state except Oklahoma and Kansas.

Commentary: ‘Never Before’ (NB4) extreme weather events … and near-misses

For the latest on the tropics, see the Eye on the Storm post from Dr. Jeff Masters filed earlier today (September 9).

Website visitors can comment on “Eye on the Storm” posts. Please read our Comments Policy prior to posting. Comments are generally open for 30 days from date posted. Sign up to receive email announcements of new postings here. Twitter: @DrJeffMasters and @bhensonweather: Bob Henson


Bob Henson is a meteorologist and journalist based in Boulder, Colorado. He has written on weather and climate for the National Center for Atmospheric Research, Weather Underground, and many freelance… More by Bob Henson

Here is a significant “ET” reported from Thursday:

Here is some more August 2021 climatology:

Here is more climate and weather news from Friday:

(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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