Inside the most extreme heat wave the Southern U.S. has faced
The summer of 2023 has featured the most intense heat in modern records averaged over the planet . June was Earths hottest on record, and the oceans are exhibiting unprecedented warmth. Far and wide, already-exceptional weather events are being pushed into record territory by the effects of human-caused climate change. In the Lower 48 states, global warming has manifested itself in a historically intense and prolonged heat wave, stretching from Californias interior to South Florida. The zone from Arizona to Texas has sat at the center, with record-shattering heat enduring for at least three weeks and showing little sign of relenting. As brutal heat wave sweeps southern U.S., more records to fall A concentrated sphere of heat, known colloquially as a heat dome, has powered the excessively high temperatures. Over the coming week, the heat dome will reach from coast to coast, inching northward and parking smack dab in the middle of the country. Over the next eight to 14 days , the National Weather Service is calling for above-normal temperatures nearly everywhere in the continental United States. Max temperature, July 18-21 Less than 80 F 80 F 90 F 100 F 110 F and greater A relentless and punishing heat dome has set temperature records over the southern United States since the beginning of July. Heat dome Concurrently, historically severe heat domes have sprawled over southern Europe and parts of Asia. Heat domes Source: NOAA Max temperature, July 18-21 Less than 80 F 80 F 90 F 100 F 110 F A relentless and punishing heat dome has set temperature records over the southern United States since the beginning of July. Heat dome Concurrently, historically severe heat domes have sprawled over southern Europe and parts of Asia. Heat domes Source: NOAA Max temperature, July 18-21 Less than 80 F 80 F 90 F 100 F 110 F A relentless and punishing heat dome has set temperature records over the southern United States since the beginning of July. Heat dome Heat domes Concurrently, historically severe heat domes have sprawled over southern Europe and parts of Asia. Source: NOAA This massive heat dome is one of several affecting the planet, bringing all-time records in parts of Europe and in China and alarmingly hot sea-surface temperatures to the Atlantic. While heat domes form every summer, recent years have featured a string of particularly anomalous heat waves. Human influence has likely increased the chance of compound extreme events since the 1950s, reads the most recent assessment from the United Nations Intergovernmental Panel on Climate Change. This includes increases in the frequency of concurrent heat waves and droughts on the global scale. In other words, what were witnessing now multiple simultaneous record-setting heat domes globally is exactly what scientists expect as increasing greenhouse concentrations from human activities warm the planet. Beneath the heat dome baking the southern U.S., numerous cities have set record highs. Reno, Nev., and Grand Junction, Colo., tied all-time records of 108 and 107 degrees on Sunday and Monday, respectively. Other cities came very close. Salt Lake City fell a degree shy of its all-time record at 106 degrees, as did Las Vegas, at 116. The nations most extreme temperatures have occurred in Arizona and Southern California. Death Valley, Calif., reached 128 degrees Sunday, two degrees from the highest temperature globally over the past 90 years. Meanwhile, Phoenix has tied or broken calendar day record highs seven times in eight days; it hit 119 degrees Wednesday and Thursday, its highest temperature since 2017 . Phoenix also registered its all-time warmest low temperature on Wednesday, dropping to just 97 degrees, to produce an average daily temperature of 108.0 degrees, its highest on record. The top 10 hottest nights on record in Phoenix have all occurred in the past 20 years, despite nearly 130 years of continuous bookkeeping. Thats probably a symptom of both warming from greenhouse gas emissions and the urban heat island effect, or the expansion of buildings and paved surfaces that elevates city temperatures. As a testament to the heat waves longevity, Phoenix has reached a high of at least 110 degrees on a record 21 straight days, while its low has been at or above 90 degrees on a record 11 nights in a row. Weather models indicate theres a chance that Phoenix will continue its string of 110-degree highs through at least the end of the month. Phoenix is also on pace to be the first American city to have an average temperature of 100 degrees or greater for any calendar month. Its not just Phoenix that cant shake the heat. El Paso has reached at least 100 degrees on a record 35 straight days and counting; the citys previous record was 23 days during a streak back in midsummer of 1994. New Orleans, which hasnt received as much attention as locations to the west, is heading for its warmest summer on record. The brutal heat has routinely combined with oppressive humidity to push heat indexes into the 100-to-108-degree range. And in Florida, Miami has had 40 days in a row with a heat index over 100, during which there was a 16-day stretch when heat index values eclipsed 105. The previous records for both were 32 days and eight days, respectively. Simply stated, there are no analogues, or comparable heat waves, in the data that rival the unusual synergy between intensity and duration that the Southern U.S. is facing right now. The Southern U.S. isnt alone. Three other heat domes have been shattering records globally: Hot weather, and even extremely hot weather, is expected during the summer. But the human influence on the climate system is supercharging extremes. If global warming increases, some compound extreme events with low likelihood in the past and current climate will become more frequent, warned the Intergovernmental Panel on Climate Change. There will be a higher likelihood that events with increased intensities, durations and/or spatial extents unprecedented in observational record will occur. In plain language, things that we havent seen before including from a magnitude and duration standpoint are now entering the realm of physical possibility, and will only become more severe as the climate warms further. Heat dome animation by Artur Galocha Our warming climate: In the Eastern U.S., the record-breaking heat wave is reaching is peaking. July was Earths hottest month , and heres where the worst, record-setting heat occurred . Use our tracker to see your citys extreme heat risk . Take a look at what extreme heat does to the human body . How to stay safe: Its better to prepare for extreme heat before youre in it. Heres our guide to bracing for a heat wave , tips for staying cool even if you dont have air conditioning , and what to know about animal safety during extreme heat . Traveling during a heat wave isnt ideal, but heres what to do if you are . Understanding the science: Sprawling zones of high pressure called heat domes fuel heat waves. Heres 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 .