The Hottest July


“Barring a major asteroid impact…it is virtually certain that
July of 2023 will be the warmest month on record…by a large margin”
Climate scientist Zeke Hausfather. 

If you’re reading these words, it’s obvious an asteroid didn’t hit the earth last month and there was no impact debris to provide shade and cooling. That means July has now been our planet’s hottest month. Not just over the last century or millennium; but in the last 120,000 years. That assessment is based on accepted scientific analysis of ocean sediments, ice cores, tree rings, and coral – a discipline called paleo-climatology. The July 2023 global heat follows the warmest June ever recorded. More than 2,300 heat records have been broken in the U.S. this summer.

Four separate “heat domes” formed over the northern hemisphere in June, extending into July. One was centered over the southwestern U.S. and northern Mexico, a second over the north Atlantic, a third over southern Europe and north Africa, and a fourth over China. Record high temperatures have included 126 degrees (125.96) Fahrenheit in Death Valley National Park as well as in Sanbao township in China, 113 degrees in Figueres, Spain along with a heat index of 152 degrees in Iran. A heat index is a measure of the combined impact of heat and humidity.

The impact of these heat domes is not limited to land. Oceanographers report an unpreceded sea surface temperature in the North Atlantic of 76.8 degrees. That exceeded the previous record set last year; even higher sea surface temperatures are expected this August. Globally, the average ocean temperature has been breaking existing records monthly since April and local ocean temperatures have been far hotter. A recording buoy in south Florida’s Manatee Bay reported what may be a world record; 101 degrees Fahrenheit (hot-tub temperatures).

“The era of global warming has ended and the era of global boiling has arrived,” remarked UN Secretary General Antonio Guterres. “The air is unbreathable, the heat unbearable and the level of fossil fuel profits and climate inaction is unacceptable.” The International Energy Agency in 2021, recognizing the link between fossil fuel use and climate change, called for an end to new oil and gas drilling. Yet governments including the United States, Great Britain, and Australia continue to grant such licenses. James Hansen, the NASA scientist who testified 35  years ago before the U.S. Senate about the cause and danger of climate change, recently termed humans “damned fools.”

The heat domes responsible for this summer’s soaring temperatures develop when high pressure systems stall. Such highs become cut off from the prevailing global wind patterns, and that isolation makes them very persistent.  Air sinks within these highs, and that sinking air also compresses and warms. Not only does that produce hot daytime temperatures, it also leads to unusually warm nighttime temperatures, reducing or eliminating the potential for temporary relief from cooling. This heating drives moisture out of the ground through evaporation, which then allows the ground and the air near it to heat more rapidly with each passing day. 

This feedback loop means heat domes do more than simply produce record temperatures, but also drought. The drought leads to crop failures and wildfires – think Canada, California, and Greece. The massive size of this year’s heat domes can even impact areas that may not suffer from extreme temperatures. Washington state is case in point. A drought emergency was declared July 24 in 12 counties – Whatcom, Skagit, Snohomish, Jefferson, Clallam, Benton, Columbia, Kittitas, Yakima, Klickitat, Okanogan, and Walla Walla. Some wells have run dry in Whatcom County. Water providers are seeking to truck in replacement supplies.

Behind these numbers are the stories of individual and collective human suffering. Montana State University professor Cascade Tuholski put it bluntly: “We know these extreme temperatures are killing people right now.” National and state parks have reported multiple heat-related deaths this summer. Physicians tell us that human bodies simply can’t perspire enough in such extreme conditions to dispel internal heat; efforts to do so elevates the stress on our hearts and kidneys in particular. Organs begin to shut down. 

That’s what happened in 2021 to a 38 year old farmworker in the Willamette Valley, Sebastian Francisco Perez. He was found unconscious in the fields on a day when temperatures exceeded 115 degrees. All attempts to revive Sebastian failed. His co-workers were faced with the wrenching task of relaying word to the extended family he worked to support. 

It’s a story that we know is repeated not merely hundreds, but thousands of times. The journal Nature Medicine reported 61,000 people died from the 2022 heat wave in Europe. This year’s death toll is expected to be far higher. And heat is not an equal opportunity killer. The greatest impact is on the young, the old, the ill, and the poor. The international affairs think tank The Atlantic Council projects the annual death toll from heat in the United States alone will rise to 60,000 men, women and children in less than three decades.

It’s becoming increasingly apparent that even those whose work and wealth insulates them from the health impacts will not be insulated from the financial impact. The same Atlantic Council study already cited quantified the U.S. cost of the 2021 heat wave at more than $100 billion. . That was the summer Seattle experienced three days of temperatures reaching or exceeding 100  degrees. This same analysis projects steadily increasing domestic labor and productivity losses reaching one-half trillion dollars by the year 2050. This includes not only agriculture, but also construction, warehouse, transportation and food services.

While all states will increasingly suffer economic impacts, the state of Texas tops the list; it accounts for almost one-third of the nation’s heat-related labor productivity losses. Not far behind is the state of Oklahoma, once represented by James Inhofe, who earned the nickname Senator Snowball. That originated from the wintry Washington D.C. day he carried a snowball inside the Senate chambers to “prove” his contention that climate change was a hoax. Ironically, Inhofe once admitted “I thought climate science was probably right, before I saw the price tag.” 

That assessment didn’t include the cost of the impact of climate change, then or now – a cost that is increasing yearly. Critics sarcastically responded that Inhofe could easily have said he thought compassion was right, before he saw the price tag, a criticism that has now been extended to the current governor of Texas. Gov. Greg Abbott recently signed a bill passed by the Texas legislature that eliminates mandatory water breaks for construction workers during heat waves, such as the ongoing one this summer that has routinely produced temperatures exceeding 110 degrees.

In contrast, Washington state requires ten minute “heat breaks” every two hours when temperatures exceed 90 degrees, and 15-minute heat breaks every two hours when temperatures exceed 100 degrees. Employers are also required to provide employees with a quart of cool drinking water each hour. Such regulations are supported by laboratory studies that demonstrate measurable medical impacts on young, fit subjects even at temperatures in the 80s.

The evidence supporting the linkage of this summer’s supercharged heat domes with global warming is strong. An authoritative assessment was just released by a group called World Weather Attribution, a consortium of leading climate scientists that examines a variety of extreme weather events. The team seeks to answer these questions: did climate change influence the likelihood, the intensity, and the impact of such events? 

The report issued July 25, based on peer-reviewed techniques, stated that heat waves the magnitude of those experienced in North America and southern Europe would have been virtually impossible without human-caused (anthropogenic) climate change; the heat waves over China were made 50 times more likely. The scientists conclude that unless the world rapidly stops burning fossil fuels, such heat waves will become more likely, possibly every two to five years.

There are exceptions to this large-scale pattern of extreme heat in the northern hemisphere. The Pacific Northwest is one such exception, particularly in the Puget Sound region. Temperatures here have been close to normal in both June and July. But Washington and Oregon represent less than 5 percent of the surface area of the United States. Withholding an effective response to widespread, continuing weather extremes based on such exceptions would be similar to withholding medical treatment to a patient suffering from burns over most, though not all of their body.

Short-term, we are left wondering whether August will bring relief. NASA’s Goddard Institute for Space Science cautions against such hopes, referencing its pessimism to the continued development of what’s called an El Nino pattern. El Nino warms the surface waters of the eastern tropical Pacific Ocean and tends to boost temperatures over much of the globe, just as its counterpart La Nina tends to act as a brake on extreme heat.  But the record summer heat of 2021 and 2022 came despite La Nina patterns. 

Now, as El Nino is still gathering strength, NASA scientists say August is likely to see more records fall, and 2024 is likely to be even warmer than this year. Our good fortune in the Puget Sound region is unlikely to last. 

Jeff Renner
Jeff Renner
Jeff Renner was a longtime weather newscaster for KING-TV.


  1. Thank you for this, Jeff, and in particular, for mentioning (and caring about) farmworkers who are struggling right now in this heat. The way you wrote about the late Sebastian Francisco Perez was moving and is evident of your compassion.

  2. Thank you for writing this astounding thought-provoking article, Jeff. We certainly are in new territory! Your description of how heat domes are created and work is very clear. “Stuck” heat is damaging the health of nature and humankind. “Stuck” thinking is damaging the logic and humanity of our responses.
    The Texas decision to throw out mandatory safety standards that provide protection for workers contending with excessive heat makes no sense. You can’t hurt the workers without hurting the workforce and everything else that connects with it.
    The pandemic gave us a chance to stop, value, and connect with our fragility and strength in a deeper way. I pray that we stop, think, and get “unstuck” by accepting and exploring our “new territory” and learning how to adjust to the changing conditions with humane solutions that respect the beauty and wholeness of life and creation.

  3. No one seems to mention that there are over 8 billion people in the world and climbing fast. In 2000 there were just over 6 billion. No wonder things are heating up.


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