Discover the Most Searing Heatwave to Ever Hit Maricopa County

Written by Kristen Holder
Updated: October 25, 2023
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Most places in the United States expect uncomfortable temperatures in the summer. However, some states burn hotter than others. What’s one of the hottest places in the United States? Let’s discover the most searing heatwave to ever hit Maricopa County now.

Where is Maricopa County?

Maricopa County has the most Arizonans living in it because Phoenix is within its borders.

Maricopa County has the most Arizonans living in it because Phoenix is within its borders.

©Alexander Lukatskiy/

Maricopa County lies in Arizona’s Sonoran Desert and it’s the most populous county in the state. It occupies the south-central section of Arizona, and it’s home to almost 4.5 million people. It’s so populous because it’s home to the Phoenix Metropolitan Area.

Over 60 percent of Arizonan residents live in Maricopa County. The county has so many people living in it that it is the fourth-largest county in the United States by population. Phoenix is the fifth largest city in the country by population, and it is also the state capital.

What Was the Most Searing Heatwave to Ever Hit Maricopa County?

The summer of 2023 hosted the hottest heatwave in Maricopa County history.

The summer of 2023 hosted the hottest heatwave in Maricopa County history.


During the summer of 2023, the most searing heatwave to ever hit Maricopa County occurred. For 31 days straight, temperatures were above 110 degrees Fahrenheit in Phoenix, AZ. This demolished the previous record of 18 days straight above 110 degrees from 1974.

This record 31-day streak took place from June 30 to July 30, 2023. July 2023 was also the hottest month ever recorded in Maricopa County’s history with an average temperature of 102.7 degrees for the month. This searing temperature average is also the hottest any United States city has ever been.

In total, 54 separate days in Maricopa County were above 110 degrees. This broke the previous record of 53 days in 2020. This makes the summer of 2023 the hottest recorded since 1893 when people began keeping track of temperatures in the area.

Summer 2023 also saw 15 days over 115 degrees though these days were not in a row. It was still a record breaker as the biggest total over 115 was in 2020 at 14 days.

Why Was It So Hot During the Summer of 2023 in Maricopa County?

It was so searingly hot in Maricopa County during the summer of 2023 because of the combined effects of El Niño and climate change. The perfect conditions created a heat dome that shifted around the southwest and southern United States for a few months.

A heat dome refers to a dome of high pressure that accumulates and sits over the same region for at least a week. As air swirls in an outward direction on high-pressure days, hot air sinks from higher in the atmosphere to fill the void. This air movement toward the ground also prevents cloud formation and almost always guarantees sunny skies and warm or hot days.

When this phenomenon continues to sit over a region, temperatures escalate as sinking hot air doesn’t move. This pocket of hotness is why the term dome is attached to these specific heatwaves. When record temperatures occur, it is often as a result of a heat dome.

El Niño’s warming effect on ocean waters in the east Pacific creates warm air, and this happened during 2023’s summer. This feeds the atmosphere with the hot air needed to create a heat dome.

Saguaros Died As a Result of the Heatwave in 2023

Fallen saguaro cactus stem lying on the ground

The searing heatwave of 2023 killed saguaros in Arizona.


The saguaros in Maricopa County had a hard time coping with 2023. The excessive heat combined with the lack of summer monsoons stressed some of the cactuses to an early death. Others lost their limbs which is a warning sign that death is on the horizon.

Saguaros are the biggest cactuses in the United States, and they only live in southern Arizona including Maricopa County and the Phoenix Metro Area. They are capable of living 200 years and growing up to 40 feet tall.

The incredibly high temperatures during the day were matched by exceptionally high temperatures as nighttime lows. Saguaros usually use the relatively cooler evenings to open pores and take in carbon dioxide for daytime photosynthesis. However, in extreme temperatures, this doesn’t occur and it weakens the cactuses.

The extremely dry conditions in 2023 also helped kill some saguaros. Dehydration weakens their tissues and makes them prone to collapse. The previous searing summer in 2020 also compromised lots of cactuses that hadn’t bounced back before the 2023 heat hit.

The Searing Heatwave of 2023 Caused Human Deaths

In 2023, 194 people died in Maricopa County as a direct result of the record-breaking heat in the region. Over 350 more deaths may have been caused by excessive heat exposure though these cases are still being investigated.

The risk of human fatalities due to the searing heatwave of 2023 motivated the medical examiner in Maricopa County to request 10 extra refrigerated containers in case a surge of bodies became overwhelming. This was the first time that the morgues had anticipated a need for additional storage since the pandemic.

The first confirmed death was on April 11 so not all heat-related deaths in Maricopa County occurred during the searing July heatwave. 40 people total died in their homes before the summer temperatures broke because they didn’t have a working air conditioner. The most common societal subgroups to die during a heatwave like this include those with mental illnesses, people who work outdoors, drug users, and the unhoused.

Schizophrenia and Heat Deaths in Maricopa County

Some medications for schizophrenia cause heat regulation issues.

Some medications for schizophrenia cause heat regulation issues.


Certain health conditions create a higher risk of heat-related death in certain people. For example, people with schizophrenia are often more sensitive to heat and dehydration as a result of the medication they are on. It has also been shown that unmedicated schizophrenics do not regulate heat as well as neurotypical people due to a difference in biology.

Around North America, as many as 13 percent of heat-related deaths during heatwaves are schizophrenics. Phoenix’s Director of Heat Response helped write a research paper about the increased hospitalization rates of schizophrenics in the city as a direct result of dangerous heat conditions.

Forty-two percent of the heat-related deaths in 2023 were unhoused citizens living on the streets in the Phoenix Metro Area. Since schizophrenia rates are high in the homeless population, it’s not a surprise that unhoused individuals are a sizeable portion of heat-related deaths in Maricopa County.

The photo featured at the top of this post is ©

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About the Author

Kristen Holder is a writer at A-Z Animals primarily covering topics related to history, travel, pets, and obscure scientific issues. Kristen has been writing professionally for 3 years, and she holds a Bachelor's Degree from the University of California, Riverside, which she obtained in 2009. After living in California, Washington, and Arizona, she is now a permanent resident of Iowa. Kristen loves to dote on her 3 cats, and she spends her free time coming up with adventures that allow her to explore her new home.

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