A multi-day heatwave is sweeping parts central South America and bringing unprecedented warmth to many large cities. Parts of Argentina are about 25 degrees above normal, while Chile, Paraguay and Bolivia are experiencing unusual warmth. Excess strain on power grids has caused widespread outages, leaving 700,000 people in the Argentine capital without electricity. This heat wave isn’t expected to end until the weekend.
The heat has been unusually pronounced for more than two weeks in Argentina, where temperatures topped 100 degrees to round out December. Although areas south of the Equator have summer, readings for this month are significantly higher than what is usual.
Buenos Aires Ezeiza Airport hit 104.2 degrees on Dec. 29, its highest December temperature on record and, at the time, highest overall temperature since 1999. The city’s observatory spiked to 41.1 degrees Celsius, or 106 degrees Fahrenheit, on Tuesday. Only one day — in January 1957 — had 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 Fahrenheit), meaning nobody there under the age of 26 has experienced temperatures this high before.
Argentina’s National Meteorological Service noted that 11 records had been smashed Tuesday. Five major cities — Punta Indio, Buenos Aires, Las Flores, El Palomar and San Fernando — registered both their highest January temperatures on record and their highest readings in at least 50 years.
The agency issued red alerts for much of the country, writing that the “extreme temperatures” would have “very dangerous” health effects.
Cordoba, a city of 3.3 million in the strip of flat plains that stretches through central Argentina, climbed to 108.5 degrees Monday.
San Antonio Oeste, 500 miles southwest of Buenos Aires and on the water, made it to 109 degrees, the station’s second-highest reading on record. The warm, dry air was blown by the westerly winds to the coast. This helped keep the marine layer at bay.
Tres Arroyos, east of Bahia Blanca, set a record at 105.3 degrees, and nearby Coronel Pringles, about 45 miles to the west-northwest, also managed a record at 103.3 degrees.
“Wear light clothing and light colors,” the weather service tweeted. “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 (40 Celsius).
Unlike in many North American heat waves, relative humidities across central Argentina were very low. This meant that the area with the highest temperatures was extremely 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. This makes heat extremely dangerous.
The extreme temperatures are the result of a heat dome, or a sprawling ridge of high pressure, that brings hot temperatures and sinking air. Air parcels that are unable to sink undergo adiabatic compression. This squeezes the air and heats them up more. The same effect is experienced by air that slides down the Andes.
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 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 phenomena, surpassing tornadoes, flooding and hurricanes in their human toll in many areas. It is hard to quantify their human impacts due to the problem of excessive mortality. This refers when people with health issues, the elderly and others who are vulnerable die from heat strokes.
Overnight minimum temperatures, which in some places may not drop below 75 or 80 degrees, 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 because of 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.