Extreme Temperature Diary- Monday July 17th, 2023/Main Topic: CAT4 Heatwave Chevron to Build Over the Southeast This Week

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: CAT4 Heatwave Chevron to Build Over the Southeast This Week

Dear Diary. We have some simultaneous historic heatwaves raging across the planet this week, so the best way to highlight Heatwave Cerberus and Heatwave Chevron is to report on what has happened with them every other day. Today it is CAT4 U.S. Heatwave Chevron’s turn to get the main topic treatment.

This week is the third week of July and is statistically the climatological peak of the warm season…or because of carbon pollution the too hot to handle season. Right on que the heat dome in association with historic Heatwave Chevron is peaking and will move eastward, affecting my neck of the woods in Atlanta this week:

Where I live hot summer weather is part of life, with most residents of Atlanta accustomed to weeks over 90°F. This week should be the hottest week of the season with maxes getting close to 100°F from Tuesday through Friday. We probably won’t see any daily records here in Atlanta because those are north of 100°F. The farther west from Atlanta one goes the more likely record heat will be encountered, however:

Luckily, Heatwave Chevron’s grasp on the Southeast will be short lived due to a strong cold front coming into the area by next weekend. The heat dome in association with the system will retrograde back to the West and will weaken at least below 597 decameters:

Here are more details from the Matthew Cappucci writing for the Washington Post. At least there are strong signs of Heatwave Chevron abating by next weekend. The longevity of the system will probably make the system a lethal killer for those susceptible to extreme heat unfortunately, though:

Historic heat wave engulfing Southern U.S. isn’t moving anytime soon – The Washington Post

Severe heat wave in southern U.S. remains entrenched as records mount

Nearly 100 million Americans are under heat alerts after temperatures approached all-time records in Reno, Las Vegas, Flagstaff and Salt Lake City on Sunday

By Matthew Cappucci

July 17, 2023 at 12:55 p.m. EDT

The southern United States is in its third week of an extreme and stubborn heat wave that refuses to budge. It continues to set records as nearly 100 million Americans remain under heat alerts from South Florida to northern Nevada.

The intensity of the heat wave probably peaked on Sunday in California’s Central Valley and the Desert Southwest. Temperatures climbed as high as 128 degrees in Death Valley and approached all-time records in Reno, Las Vegas, Flagstaff and Salt Lake City. Although temperatures won’t be quite as high in the Southwest in the coming days, it will still be dangerously hot, and more records could be set.

Meanwhile, in parts of the South and Southeast, above-normal temperatures and sauna-like humidity will make it feel intolerably hot, with triple-digit heat indexes continuing for days.

High temperatures Monday as forecast by the National Weather Service. (Pivotal Weather)

The “heat dome” over the Southern United States is one of several across the Northern Hemisphere that are bringing high-impact heat to Europe and Asia as well. Sunday featured a high temperature of 122 degrees in Sinboa, China, the country’s highest temperature ever observed and the highest recorded north of 40 degrees latitude globally.

In Europe, the Italian island of Sardinia could approach 117 degrees on Tuesday, while Rome nears 108 degrees — which would eclipse Rome’s all-time record by 3 degrees. In the Middle East, Persian Gulf International Airport in Iran posted a suffocating heat index of 152 degrees Sunday.

It’s well established that the frequency, intensity, size and duration of high-end heat events is increasing because of human-caused climate change. The southern U.S. heat wave has occurred amid the hottest days on record for the planet; every day since July 3, the Earth’s average temperature has surpassed the temperature that held the previous record.

The forecast

The heat dome expands and languishes across the southern United States over the next five days, as simulated by the American GFS model. (WeatherBell)

The heat dome — a persistent lobe of hot, sinking air that is responsible for the excessive temperatures — isn’t going anywhere any time soon. In fact, it’s expected to consolidate and intensify some again while shifting east.

That will allow temperatures to decline slightly for a few days in California, but readings are spiking once again in Texas and across the south central United States. As the heat slowly progresses east and builds, more records are in jeopardy. Here’s where records will be challenged:


  • Albuquerque is set to tie a record of 104, set in 1980.
  • Tucson may fall just a degree shy of its 111-degree record set in 2005.
  • Austin will approach a record of 105 set in 1984, but could fall just shy.
  • Corpus Christi, Tex., is forecast to hit 100 degrees, tying a record set in 1998.
  • San Angelo, Tex. is expected to reach the record of 106, set in 1989.
  • San Antonio is predicted to fall a degree shy of a record, only hitting 104.


  • Tucson should break a record and make it to 110; the number to beat is 109, set in 1992.
  • Austin is forecast to break a record and make it to 105; the prior record, set last year, was 103
  • Corpus Christi, Tex. will probably tie a record of 99, set in 2011.
  • Laredo and San Angelo, Tex., should both make it to 108, which would fall one degree short of the record in Laredo but would break a record by one degree in San Angelo.
  • Wichita Falls, Tex., is aiming for 109, which is one degree short of last year’s record.

Phoenix is forecast to challenge several records this week. It also is set to easily surpass its record-long streak of 18 straight days at or above 110 degrees, set in June 1974. This past Sunday was the city’s 17th consecutive day in that range, and it’s expected to reach at least 112 every day through this coming Sunday.

The heat is helping exacerbate several ongoing wildfires across the Southwest, including California’s Rabbit Fire, which has burned 7,950 acres southeast of San Bernardino. It is 35 percent contained. More than a dozen blazes were also burning across Arizona.

Records set Sunday

California and the West

Sunday featured numerous weather records across the West and Desert Southwest. Death Valley set a calendar-day record at 128 degrees, falling just shy of 130 degrees, the highest temperature observed globally since at least 1931. The nearby station of Badwater remained at 120 degrees after midnight, the Earth’s highest temperature ever observed so late at night, according to weather historian Maximiliano Herrera.

How bad is heat risk near you?

(The Washington Post)

We’re tracking dangerous heat waves across the United States daily. Look up your city to see extreme heat risks near you.

Reno reached 108 degrees Sunday, matching its highest temperature ever observed. Kingman, Ariz., set an all-time record of 114.

Flagstaff (high of 96), Las Vegas (116) and Salt Lake City (106) missed all-time highs by one degree, but set calendar-day records.

Phoenix didn’t set a record high on Sunday but has seen low temperatures only bottom out in the 90s a record 8 days in a row.

To the north, in California’s Central Valley, Sacramento and Stockton set calendar-day records of 109 on Sunday. The heat made it as far north as the Columbia River Basin, including Idaho Falls, which nabbed a calendar-day record of 98.

Plains and Southeast

Across Texas, the southern Plains and the Southeast, high temperatures mostly didn’t make it to record values, but, coupled with the humidity, were yielding heat indexes in the 105-to-115-degree range. The humidity was also preventing overnight lows from falling much, which lead to record warm overnight temperatures.

Key West only dropped to 85 degrees Sunday morning, a record warm minimum for the date. Records at Key West date to 1872. Alma, Ga., logged an overnight low of 76, which was a record. College Station, Tex., had a record warm low of 81 degrees.

More on extreme heat

Our warming climate: In the Southern U.S., a sweltering heat wave isn’t moving anytime soon. On Sunday, the historic heat wave reachedits maximum intensity across the Southwest and California. It’s not just you ⁠— summers in the U.S. are getting hotterLook up your city to see your extreme heat risk with our tracker. Take a look at what extreme heat does to the human body.

How to stay safe: It’s better to prepare for extreme heat before you’re in it. Here’s our guide to bracing for a heat wave, tips for staying cool even if you don’t have air conditioning, and what to know about animal safety during extreme heat. Traveling during a heat wave isn’t ideal, but here’s what to do if you are.

Understanding the science: Sprawling zones of high pressure called heat domes fuel heat waves. Here’s how they work. You can also read more about the link between weather disasters and climate change, and how leaders in the U.S. and Europe are responding to heat.

By Matthew Cappucci Matthew Cappucci is a meteorologist for Capital Weather Gang. He earned a B.A. in atmospheric sciences from Harvard University in 2019, and has contributed to The Washington Post since he was 18. He is an avid storm chaser and adventurer, and covers all types of weather, climate science, and astronomy. Twitter


Here are some other “ET’s” recorded from around the planet the last couple of days, their consequences, and some extreme temperature outlooks, as well as any extreme precipitation reports:

Here is more climate and news from Monday:

(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.)

Today’s News on Sustainable and Traditional Energy from Fossil Fuel:

More Environmental Stuff:

More from the Weather Department:

More on other science and the beauty of Earth and this universe:

If you like these posts and my work on record temperature ratios, 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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