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(STACKER) – Extreme heat kills more people every year than all other serious weather events. Dangerously high temperatures can quickly overwhelm victims without much warning and can cause death or grave illness virtually anywhere in the country. Those who work outdoors are especially vulnerable, as are the elderly, the infirm, small children, and pets—especially those that are even briefly left in vehicles.

Extreme heat disrupts agriculture and puts enormous pressure on utilities and electrical grids. It makes fires much more likely both in the wild and in structures. The hottest days are also a heavy lift for municipalities, which are forced to open cooling centers, corral homeless populations, and put extra emergency responders on the streets.

There was a time when record-breaking heat was a big deal and when the hottest temperature records stood unchallenged for decades. Today, those records are commonly broken shortly after being set and then quickly broken again. Just as with hurricanes, droughts, and other dangerous weather, extreme heat events are becoming both more frequent and more severe as the effects of climate change become inescapable. Across the country, the hottest days are getting hotter, the coldest days are getting warmer, and summer is encroaching further and further into fall.

In order to find the cities facing more extreme heat in recent summers, Stacker analyzed data in a July 2020 report from Climate Central, a nonprofit climate communication organization. The report analyzed historical temperature data for 243 cities from NOAA’s Applied Climate Information System over a study period from 1970 to 2019. To select the primary temperature threshold for each city, an “extremely hot day” is defined as the highest 5 degree Fahrenheit increment temperature that occurred at least four days every year during more than half of the years of the study period (1970-2019). Change in the number of “extreme heat” days is based on linear regression. When available, contextual summer weather data from 1970 to 2019 from the National Oceanic and Atmospheric Administration’s Time Series database is provided.

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#50. Cheyenne, Wyoming

– Increase in extreme heat days: 12.2
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 64.4° F
— Summer maximum: 91.6° F (July 2003)
— Summer minimum: 39.4° F (September 1971)

Cheyenne is no stranger to blazing heat, but the weather there recently has been nothing short of extreme. The region just emerged from its hottest summer in history after temperatures routinely topped 90 degrees in August. Then, on Sept. 8, Mother Nature roared the other way and handed Cheyenne its earliest snowfall on record.

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#49. Columbus, Ohio

– Increase in extreme heat days: 12.8
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 71.4° F
— Summer maximum: 91.1° F (July 2012)
— Summer minimum: 50.6° F (September 1976)

The average temperature in Columbus rose by 2.3 degrees between 1951-2012, according to a report by the University of Michigan Climate Center and the Great Lakes Integrated Sciences and Assessment. Columbus got warmer faster than both the country and the world, and temperatures are expected to rise by an additional 3-5 degrees by the middle of the century. In response, the city adopted the Columbus Climate Adaptation Plan, which calls for things like the creation of connected cooling centers.

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#48. Las Cruces, New Mexico

– Increase in extreme heat days: 13.3
– Extreme heat threshold: 100° F

Located inside the Chihuahuan Desert, the city of Las Cruces is well accustomed to intense heat. In 2017, New Mexico State University nursing students collaborated with the city to create a comprehensive story map for seniors and other vulnerable populations. This year, temperatures there reached the high 90s by April and in May, the city sweltered through eight consecutive days of record heat. By mid-July, the start of the hottest part of the year, Las Cruces was choking under several straight days of 100-plus degree temperatures, with officials scrambling to protect seniors, small children, the indigent, and other high-risk groups.

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#47. Alexandria, Louisiana

– Increase in extreme heat days: 13.3
– Extreme heat threshold: 95° F

In July 2019, Alexandria began with an intense heatwave and by the middle of the month, the city was canceling events during a stretch of days that earned the highest possible heat index warning of “extreme danger.” The heat index reached or even topped 110 degrees for several days straight, driving the city and much of the region into a weather-induced lockdown.

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#46. Atlantic City, New Jersey

– Increase in extreme heat days: 13.4
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 72.2° F
— Summer maximum: 91.3° F (July 2011)
— Summer minimum: 53.4° F (September 1978)

Like much of the country, the South Jersey Shore seems to break its own heat records every summer. On July 23, 2019, temperatures in Atlantic City topped the all-time high. Almost exactly one year later on July 27, 2020, the region was trapped in an extended heatwave that peaked with multiple consecutive days in the high 90s with the heat index moving into triple digits. In places like the Jersey Shore, extreme heat is not only dangerous for people and pets, but it disrupts the critical summer tourism season.

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#45. Chattanooga, Tennessee

– Increase in extreme heat days: 13.9
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 78.0° F
— Summer maximum: 97.8° F (July 1993)
— Summer minimum: 56.9° F (September 1984)

Chattanooga is America’s No. 6 fastest-warming city. In Tennessee, where hundreds of thousands of residents are vulnerable to heat-related danger, officials are bracing for an increase from the 10 annual heat danger days it currently experiences to 55 in 2050. Since the dewpoint temperature is rising, the already muggy state is getting muggier in the summers, which increases the length and intensity of mosquito season, and heightens the transmission risk for pathogens like the Zika virus.

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#44. El Paso, Texas

– Increase in extreme heat days: 14.4
– Extreme heat threshold: 100° F
– Summer statistics:
— Summer average: 81.3° F
— Summer maximum: 102.6° F (June 1980)
— Summer minimum: 60.9° F (September 1976)

According to the El Paso City-County Office of Emergency Management, “Extreme heat often results in the highest number of annual deaths among all weather-related hazards.” The West Texas border town, located in the Chihuahuan Desert, earned its first excessive heat warning in 25 years in early July as El Paso endured several days straight of triple-digit temperatures that reached 109 degrees at least two days in a row.

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#43. Birmingham, Alabama

– Increase in extreme heat days: 14.4
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 78.5° F
— Summer maximum: 98.3° F (August 2007)
— Summer minimum: 59.3° F (September 1981)

Both heat and drought battered Birmingham in the summer of 2019, culminating in the hottest, driest September on record. A year later in July 2020, officials were advising residents to stay indoors once again as heat that was excessive even by the standards of Central Alabama scorched the region. In that part of the South, dangerous heat events not only raise the temperature but also the UV index while increasing the likelihood of dangerous and deadly thunderstorms.

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#42. Denver, Colorado

– Increase in extreme heat days: 14.6
– Extreme heat threshold: 95° F

According to NPR, Denver residents are becoming resigned to the reality of extreme heat as the new normal—but heat isn’t the only factor in the wild weather that the region has come to expect. During an extraordinary couple of days in early September, Denver experienced both record heat and record snowfall back to back in one 48-hour period.

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#41. New Orleans, Louisiana

– Increase in extreme heat days: 14.9
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 82.0° F
— Summer maximum: 96° F (August 2011)
— Summer minimum: 68.4° F (September 1975)

Several Louisiana cities are among those in the United States that are experiencing an increase of at least two weeks of extreme heat days compared to 50 years ago, with a few gaining more than a month of dangerous heat days. New Orleans is getting about 15 more days with temperatures above 95 degrees and a full 28 days when the mercury breaches 90 degrees.

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#40. Abilene-Sweetwater, Texas

– Increase in extreme heat days: 14.9
– Extreme heat threshold: 100° F

In August 2019, a local ABC affiliate reported that a window in Abilene spontaneously shattered as a result of the extreme heat plaguing the region—temperatures had reached 104 degrees that day. Almost precisely one year later in August 2020, the same ABC affiliate reported that temperatures were once again deep into the triple digits and breaking heat records for two days straight—the thermometer reached 109 in some towns in the region.

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#39. West Palm Beach, Florida

– Increase in extreme heat days: 15.1
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 82.2° F
— Summer maximum: 93° F (June 1998)
— Summer minimum: 71.5° F (June 1971)

Climate change has certainly contributed to the five-degree increase in nighttime temperatures that West Palm Beach has experienced over the last decade alone, but it’s not the only culprit. Overpopulation—and the massive expanses of concrete that come with it—has transformed the region into a paved oven. The city is now participating in a greening program that attempts to increase the number of trees and reduce the stunning volume of heat-absorbing steel and concrete that now smothers much of the city.

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#38. Reno, Nevada

– Increase in extreme heat days: 15.2
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 70.6° F
— Summer maximum: 98° F (July 2018)
— Summer minimum: 37.8° F (September 1970)

According to the Reno Gazette-Journal, “extreme heat is killing Nevadans, and it’s only getting hotter.” Nevada is no stranger to desert heat, but consistently rising temperatures have dramatically increased the number of annual extreme heat days not only in Reno but also in places like Las Vegas and Tahoe, which now challenge or break their own heat records nearly every summer.

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#37. Memphis, Tennessee

– Increase in extreme heat days: 15.5
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 79.5° F
— Summer maximum: 98.3° F (August 2007)
— Summer minimum: 60° F (September 1974)

At least 175 people have died as a direct result of excessive heat since 1980 in Shelby County, home to Memphis, although the true number is likely much higher—and it will almost certainly continue to rise in the future. In 1969, Memphis experienced 52 days of 90-plus-degree heat but by 2050, that number is expected to climb to 90. That’s about one day in four.

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#36. Salisbury, Maryland

– Increase in extreme heat days: 15.7
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 73.1° F
— Summer maximum: 91.1° F (July 2010)
— Summer minimum: 54.6° F (September 1984)

A 2019 news report out of Salisbury put the ripple effects of extreme heat on display by profiling a group that isn’t usually included with the very old, the very young, the infirm, and pets on the usual lists of vulnerable populations. Residents of Delmarva and the entire Mid-Atlantic are well-accustomed to hot, sticky summers and long heatwaves—few more so than construction workers. Nonessential work ground to a halt as laborers who couldn’t stay home struggled to move 300-degree materials in 95-degree weather that generated 150-degree surface temperatures.

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#35. Colorado Springs, Colorado

– Increase in extreme heat days: 15.8
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 67.7° F
— Summer maximum: 92.9° F (July 2003)
— Summer minimum: 44.1° F (September 1971)

In Colorado Springs, extreme heat conditions bring risks much greater than stalled construction projects. Excessive heat, particularly when combined with high winds, bring red flag warnings, which indicate a high risk for the kinds of fires that are currently incinerating Colorado’s regional neighbors.

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#34. Tampa, Florida

– Increase in extreme heat days: 16.4
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 83.1° F
— Summer maximum: 93.7° F (June 1998)
— Summer minimum: 72.4° F (June 1976)

Like so many hot cities with heat records that should be hard to break, Tampa keeps breaking them. Most recently in June, Tampa hit an all-time high of 99 degrees as part of a multi-day heat advisory. It’s also maintaining a streak of nine warmer-than-average winters in a row.

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#33. Palm Springs, California

– Increase in extreme heat days: 16.5
– Extreme heat threshold: 110° F

Just as in Tampa, heat records in Palm Springs don’t last very long anymore. On Aug. 14, 2020, Palm Springs shattered the all-time high temperature by three degrees when the mercury climbed to 120—the previous 117-degree record was set in 2019. The Sunday before, it reached 113, missing by two degrees the 115-degree record for that date in 2016.

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#32. Bryan-College Station, Texas

– Increase in extreme heat days: 17
– Extreme heat threshold: 100° F

In March, temperatures in Texas’ Brazos Valley were approaching 90 degrees and Bryan-College Station was already near the record set there in 2019 when the temperature topped out at 94 degrees. It was a phenomenon not seen in more than a century since the thermometer last reached 90 in 1917 during World War I.

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#31. Tucson, Arizona

– Increase in extreme heat days: 17.8
– Extreme heat threshold: 105° F
– Summer statistics:
— Summer average: 85.1° F
— Summer maximum: 105.4° F (June 2013)
— Summer minimum: 64.1° F (June 1991)

Climate change and the urban heat island effect triggered record temperature averages every month this summer not only in Tucson but throughout much of Arizona. It’s a harbinger of things to come. Experts predict the region will be hit with a double whammy—as temperatures continue to rise, critical monsoon rains are expected to decline by 30%-40% by the end of the century.

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#30. Erie, Pennsylvania

– Increase in extreme heat days: 17.9
– Extreme heat threshold: 85° F
– Summer statistics:
— Summer average: 68.7° F
— Summer maximum: 85.4° F (July 2011)
— Summer minimum: 52.1° F (September 1974)

Brutal heat and high humidity sent the heat index soaring to as high as 100 degrees—15 degrees above the extreme heat threshold—in the Erie region this summer. Officials issued warnings and urged vulnerable residents to stay indoors as the metro broke several historic temperatures on consecutive days.

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#29. Raleigh-Durham, North Carolina

– Increase in extreme heat days: 18.2
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 76.1° F
— Summer maximum: 96° F (August 2007)
— Summer minimum: 56.5° F (September 1981)

It’s standard operating procedure for Raleigh-Durham to experience unusually hot days and extended spells of unusually hot days, but both are becoming far more usual than they’ve ever been. The metro now suffers through 18 more days per year on average that pass the 95-degree extreme heat temperature threshold compared to 1970.

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#28. Yuma-El Centro, Arizona

– Increase in extreme heat days: 18.5
– Extreme heat threshold: 110° F
– Summer statistics:
— Summer average: 90.9° F
— Summer maximum: 110.4° F (August 2011)
— Summer minimum: 67° F (September 1985)

Scorching heat is so common in the desert Southwest that the Arizona Department of Health Services created an in-depth guide to prepare for and survive extreme heat events—and in Arizona, survival is far from guaranteed. More than 1,500 people died in the state as a direct result of heat exposure between 2000-2012.

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#27. Lexington, Kentucky

– Increase in extreme heat days: 18.7
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 73.5° F
— Summer maximum: 93.4° F (July 2012)
— Summer minimum: 53.2° F (September 1976)

A warming climate and heat spells that are both more frequent and more severe have recently sent some long-held records packing in Kentucky. In September 2019, Lexington broke a 119-year-old record when the temperature reached 100 degrees in the first month of fall. Also that day, Louisville broke a record high that had stood since 1897.

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#26. Lafayette, Louisiana

– Increase in extreme heat days: 19.7
– Extreme heat threshold: 95° F

Two of Lafayette’s five warmest days and one of its five warmest months on record came in the year 2000 or later. By contrast, every single one of its five coldest days and five coldest months occurred in 1989 or earlier.

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#25. Columbus, Georgia

– Increase in extreme heat days: 20.6
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 80.8° F
— Summer maximum: 98.3° F (July 1986)
— Summer minimum: 63.8° F (September 1981)

At the end of September 2019, residents of the Columbus region were expecting crisp fall weather. What they got instead was extreme heat that reached into the triple digits, shattering a record that had previously stood for nearly a century. Like their counterparts in so many other already hot regions, Columbus residents are getting used to summer weather stretching out into what should be autumn.

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#24. Columbia, South Carolina

– Increase in extreme heat days: 21.3
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 80.1° F
— Summer maximum: 99.7° F (July 1986)
— Summer minimum: 60.2° F (September 1984)

Georgia is hardly alone in experiencing an emerging trend of long, extended summers with hot weather that gobbles up more and more of the fall season. Just to the north in South Carolina, Columbia wrapped up a historically hot and dry summer in 2019 with 27 fall days that topped 90 degrees—several crept into triple digits—before fall was even half over. Three of the state’s top five such records have been set within the last decade.

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#23. Beaumont, Texas

– Increase in extreme heat days: 21.5
– Extreme heat threshold: 95° F

The East Texas Gulf Coast city of Beaumont is known for its hot weather—90-degree days are possible there for 10 months of the year excluding only January and February. 100-degree days are common from May to September.

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#22. Baton Rouge, Louisiana

– Increase in extreme heat days: 21.6
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 80.7° F
— Summer maximum: 96.8° F (August 2011)
— Summer minimum: 63.8° F (September 1975)

In August 2019, Baton Rouge residents received something that’s rare in a place so thoroughly accustomed to devilish temperatures—a heat advisory. For the first time since 2015, officials warned residents of the deadly dangers that would accompany the furnace-like conditions that settled over the area, sending the heat index as high as 113 degrees.

Billy Hathorn // Wikimedia Commons

#21. Odessa, Texas

– Increase in extreme heat days: 21.8
– Extreme heat threshold: 100° F

In 2019, Odessa was just one part of a huge swath of West Texas that was gripped by a historic heatwave that broke all-time regional records for August. In the Central Permian Basin, temperatures climbed to 113 degrees. It reached 115 in the Pecos and Rio Grande River valleys.

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#20. Knoxville, Tennessee

– Increase in extreme heat days: 22.1
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 75.6° F
— Summer maximum: 94.9° F (July 1993)
— Summer minimum: 55° F (September 1984)

Like much of Tennessee, the Knoxville region frequently suffers from both extreme heat and high humidity at the same time. The combination contributes to a much higher heat index, more dangerous conditions, and an increased likelihood of severe thunderstorms.

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#19. Lake Charles, Louisiana

– Increase in extreme heat days: 22.2
– Extreme heat threshold: 95° F

In Lake Charles, excessive heat season happens to coincide with hurricane season—and the two don’t play well together. Most recently at the very start of September, victims of Hurricane Laura found themselves living in ravaged structures, often without electricity or air conditioning, as a crushing heatwave settled over the devastation. On some days, the heat index reached 110 degrees.

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#18. Monroe, Louisiana

– Increase in extreme heat days: 22.3
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 80.3° F
— Summer maximum: 100.9° F (August 2011)
— Summer minimum: 60.2° F (September 1975)

Like New Orleans, Monroe was listed among the American cities that are experiencing at least two full weeks more of extremely hot days than they were 50 years ago. Monroe, along with Lake Charles and Baton Rouge, gets 22 more days above 95 degrees today than it did in 1970.

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#17. San Antonio, Texas

– Increase in extreme heat days: 23.2
– Extreme heat threshold: 100° F
– Summer statistics:
— Summer average: 82.8° F
— Summer maximum: 101.5° F (August 2011)
— Summer minimum: 64.1° F (September 1974)

South-Central Texas’ San Antonio had a historic summer season in terms of heat when temperatures—not the heat index, but the actual temperature—soared to 106 degrees. The moment triggered an excessive heat warning from the National Weather Service. It was only the second time in the city’s long and storied history that the agency issued such an advisory, which is reserved only for the most extreme events where temperatures top 105 degrees and the heat index hits 113.

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#16. Huntsville, Alabama

– Increase in extreme heat days: 23.2
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 78.2° F
— Summer maximum: 99.6° F (August 2007)
— Summer minimum: 57.1° F (September 1981)

Huntsville is one of the rare cities where at least one old weather record has withstood the test of global warming. Its most extreme heat event took place in 1952 when temperatures reached 106 degrees on both July 28 and 29.

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#15. Tri-Cities, Tennessee

– Increase in extreme heat days: 24.7
– Extreme heat threshold: 90° F

In 2019, Tri-Cities broke a record that had stood for 80 years when a 96-degree day knocked a 95-degree that had stood since 1939 off of its perch. Twenty-four hours later, it broke the next day’s record, which had stood since 1964.

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#14. Louisville, Kentucky

– Increase in extreme heat days: 25.5
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 76.3° F
— Summer maximum: 96.1° F (August 2007)
— Summer minimum: 55.4° F (September 1974)

Few cities are more familiar with the shrinking-autumn phenomenon than Louisville, which has a long history of extreme heat events, terrible droughts, and extended heatwaves. On Sept. 30, 2019—the very last day of the first month of fall—temperatures in the city approached 100 degrees.

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#13. Bluefield, West Virginia

– Increase in extreme heat days: 25.5
– Extreme heat threshold: 85° F

Like so many places affected by climate change, Bluefield isn’t only getting warmer, its weather is becoming more extreme. Although only a dozen cities are seeing greater increases in extreme heat, Bluefield made news in 2019 for surprises on the other end of the climate spectrum. On Nov. 12 and 13, the city shattered back-to-back cold-weather records when it turned in a 6-degree day followed by a 13-degree day.

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#12. Augusta, Georgia

– Increase in extreme heat days: 25.5
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 79.7° F
— Summer maximum: 100.2° F (July 1993)
— Summer minimum: 58.7° F (September 1981)

In 2019, the Augusta Chronicle cited a report that painted a bleak picture for the future of the paper’s home city. Without action by century’s end, the report concluded, Augusta will experience two weeks of “dangerous heat” index days that exceed the 127-degree maximum that the National Weather Service uses as its measurement ceiling.

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#11. Atlanta, Georgia

– Increase in extreme heat days: 26.9
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 78.0° F
— Summer maximum: 96.6° F (August 2007)
— Summer minimum: 61.2° F (September 1982)

In 2019, Atlanta was crushing heat records as temperatures climbed to 96 degrees through the beginning of October. The city usually gets 37 days of 90-plus-degree days per year, but in 2019, temperatures broke the 90-degree barrier at least 87 times.

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#10. Tyler, Texas

– Increase in extreme heat days: 29.5
– Extreme heat threshold: 95° F

Oppressive heat has long been a staple of summers in Tyler, but in 2018—as with so many other hot regions of America—a long-standing record finally fell victim to rising global temperatures. On July 2 that year, temperatures hit 103 degrees—enough to break the record of 102, which was set in Tyler in 1896. That, however, soon felt reasonable as temperatures climbed to 107 later that same week.

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#9. Shreveport, Louisiana

– Increase in extreme heat days: 30.7
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 81.1° F
— Summer maximum: 104.4° F (August 2011)
— Summer minimum: 61.9° F (September 1975)

Like New Orleans and Monroe, Shreveport is yet another Louisiana city that gets at least two weeks more of extremely hot weather today than it did 50 years ago. Shreveport now experiences 31 more days—a full month—that reach 95 degrees or higher than it did in 1970.

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#8. San Angelo, Texas

– Increase in extreme heat days: 33.2
– Extreme heat threshold: 100° F

Thanks to the presence of the Chihuahuan Desert, people in the region of San Angelo have long grown accustomed to crippling heat. In mid-July, however, the National Weather Service was forced to issue an Excessive Heat Warning, not just for San Angelo, but for essentially all of West Texas. Record-high temperatures of 105-110 degrees were the rule, not the exception, creating dangerous and potentially deadly conditions.

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#7. Houston, Texas

– Increase in extreme heat days: 33.5
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 83.2° F
— Summer maximum: 100.1° F (August 2011)
— Summer minimum: 67.8° F (September 1975)

On July 16, 2019, the Houston Chronicle reported on a study that predicted more bouts of extreme heat for not only Houston but for Texas as a whole in the coming years. Almost exactly one year later on July 13, 2020, the prophecy came true when triple-digit temperatures combined with high humidity blanketed the region for days on end. In several cases, the heat index broke 100 degrees by 10 a.m., remained in triple digits for eight hours, and peaked at well over 110 degrees.

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#6. Tallahassee, Florida

– Increase in extreme heat days: 34.1
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 80.8° F
— Summer maximum: 97.5° F (June 1998)
— Summer minimum: 65.6° F (September 1981)

Anyone who has visited the Florida Panhandle in the summer is familiar with the crushing heat that’s common fare in Tallahassee—but even North Florida veterans might not be ready for what’s likely to come in the near future. In 2019, a local ABC affiliate reported on a study that predicted Tallahassee will get 50 days a year with the heat index above 105 degrees by 2036 if action is not taken to mitigate the effects of global warming.

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#5. Corpus Christi, Texas

– Increase in extreme heat days: 37.1
– Extreme heat threshold: 95° F
– Summer statistics:
— Summer average: 83.0° F
— Summer maximum: 98.8° F (August 2009)
— Summer minimum: 67.7° F (September 1974)

Rounding out the top five is Corpus Christi in the state of Texas, which is home to four of the final five entries on this list. On June 6, the city went through the annual ritual of opening cooling centers to prevent death and illness from the crushing heat and humidity that settled over the city. Exactly one month later on July 6, Corpus Christi officials did the exact same thing for the exact same reason.

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#4. Victoria, Texas

– Increase in extreme heat days: 44
– Extreme heat threshold: 95° F

Over the last several years, heat records have been broken in Victoria and the surrounding region, only to be quickly broken again. Most recently in 2019, much of South Texas was under a heat advisory as temperatures broke into triple digits four times as early as Aug. 7 with more 100-plus days to come. During those stretches, the heat index routinely rose above 110 degrees.

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#3. Austin, Texas

– Increase in extreme heat days: 44.3
– Extreme heat threshold: 100° F
– Summer statistics:
— Summer average: 83.5° F
— Summer maximum: 104.8° F (August 2011)
— Summer minimum: 64.1° F (September 1974)

In 2013, Austin set a new daily heat record when temperatures reached 105 degrees—but as is the case in much of the country, heat records don’t last long nowadays in Central Texas. On the same date in July 2020, the temperature—not the heat index—climbed to 108 degrees.

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#2. McAllen, Texas

– Increase in extreme heat days: 49.9
– Extreme heat threshold: 100° F

McAllen and much of the rest of the Rio Grande Valley were under an Excessive Heat Warning in June 2019 as temperatures reached 106 degrees and the heat index climbed to a deadly 119 degrees—but that was hardly the start of it. Earlier this year, summer seemed to precede spring in the RGV when McAllen broke a record set in 1955 after logging a 102-degree day in April.

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#1. Miami, Florida

– Increase in extreme heat days: 77
– Extreme heat threshold: 90° F
– Summer statistics:
— Summer average: 83.2° F
— Summer maximum: 92.5° F (June 1998)
— Summer minimum: 73.7° F (June 1972)

Few states face a greater risk of devastation related to climate change than Florida, and Miami is among the most vulnerable of all cities. Miami broke heat records and then broke them again over and over during the summer of 2019, and that pattern offers a glimpse of what’s to come across the entire state. According to the Miami New Times, Florida can expect its current average of 125 days of extreme heat to grow to 166 such days by midcentury and 186 by 2021 if global warming is allowed to continue unabated.

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This report was contributed by Stacker.