A multiday heat wave is gripping parts of central South America, bringing record warmth to several large cities. Parts of Argentina are about 25 degrees above normal, while parts of Chile, Paraguay, and Bolivia are experiencing unusual warmth. Excess strain on power grids have caused widespread outages, leaving 700,000 people without power. The heat wave doesn’t appear to be letting up until this weekend.
The heat has been unusually pronounced for more than two weeks in Argentina, where temperatures topped 100 degrees Fahrenheit to round out December. Areas south of the equator are experiencing summer at present, but readings are still wildly off base for what would typically be observed this time of year.
Buenos Aires Ezeiza Airport hit 104.2 degrees Fahrenheit on Dec. 29, its hottest December temperature on record and, at the time, highest overall temperature since 1999. The city’s observatory later spiked to 41.1 degrees Celsius, or 106 degrees Fahrenheit, on Jan. 11. Only one day - in January of 1957 - snagged a higher temperature in nearly 115 years of record-keeping.
Maximiliano Herrera, a climate historian who tracks international temperature records, described Tuesday as “a historic day in Buenos Aires.” The recent heat wave also represents the first time since 1995 that the Argentine capital has seen temperatures exceeding 40 degrees Celsius (104 degrees Fahrenheit), meaning nobody there under the age of 26 has experienced temperatures this high before.
Argentina’s Servicio Meteorológico Nacional, akin to the National Weather Service, noted that 11 records had been smashed on Tuesday. Five major cities, including Punta Indio, Buenos Aires, Las Flores, El Palomar, and San Fernando all witnessed both their highest January temperatures on record and their highest readings in at least the past 50 years.
The agency issued red alerts for much of the country, writing that the "extreme temperatures" would have "very dangerous" effects on health.
Córdoba, a city of 3.3 million located in the strip of flat plains that stretches through central Argentina, climbed to 108.5 degrees Fahrenheit on Monday.
Farther to the west in San Juan, a city in the lee of the Andes Mountains east of the Chilean border, temperatures unofficially may have reached 111 degrees Fahrenheit.
San Antonio Oeste, 500 miles southwest of Buenos Aires and on the water, made it to 109 degrees Fahrenheit, the station’s second-highest reading on record. Westerly winds helped blow extremely warm air all the way toward the coast, fending off the more moderate marine layer.
Tres Arroyos, east of Bahía Blanca, set an record at 105.3 degrees Fahrenheit, and nearby Coronel Pringles, about 45 miles to the west-northwest, also managed a record at 103.3 degrees Fahrenheit.
"Wear light clothing and light colors," tweeted Argentina's national weather service. "Eat lightly. Don't expose yourself to the sun."
It was also exceptionally hot in neighboring Paraguay and Uruguay, where temperatures soared above 104 degrees Fahrenheit (40 degrees Celsius).
Unlike in many North American heat waves, relative humidities across central Argentina were very low. That meant the air where the hottest conditions were ongoing was bone dry.
In scorching environments characterized by dry conditions, people outdoors won't actively notice sweat accumulating on their bodies - instead, the atmosphere will evaporate it before it can collect, desiccating an individual before they even notice they're dry. That makes the heat especially dangerous.
The crazy temperatures are the result of a heat dome, or a sprawling ridge of high pressure, which brings hot temperatures and sinking air. Parcels of air that sink are subject to a process called adiabatic compression, which squeezes air pockets and causes them to heat up even more. Air that "downslopes," or slides down the Andes, experiences the same phenomenon, magnifying the effect.
Since air expands when it's heated, heat domes can cause the lower atmosphere to bulge and expand vertically. The heat dome over Argentina thus far has boosted the atmosphere's "halfway" mark of density about 415 feet higher than average.
The heat has instigated widespread power outages resulting from increased electrical demand due to cooling. Reuters reports that at least 700,000 customers have been affected.
The heat wave could eventually affect agriculture too; Argentina is among the world's top exporters of soybean and corn.
Heat waves are among the deadliest weather phenomenon, surpassing tornadoes, flooding and hurricanes in their human toll in many areas. Quantifying their exact human impact is difficult due to the issue of "excess mortality," which occurs when elderly, those with preexisting health conditions and other vulnerable populations die prematurely due to the heat.
Overnight minimum temperatures, which in some places may not drop below 75 or 80 degrees Fahrenheit, can prevent the body from having an opportunity to cool down and reset before the next day of heat.
Human-induced climate change is amplifying the frequency and intensity of heat domes and, subsequently, bolstering the impacts of extreme heat. Last year was the fifth hottest on record globally, according to the Copernicus Climate Change Service of the European Union and ocean warmth hit a record due to the uptake of greenhouse gases spewed by human activity.
While the heat in Argentina looks likely to subside by this weekend, it’s the latest episode to fit into an alarming pattern illustrating the effects of human-induced climate change.