Why it’s so hot in Brazil, where a Taylor Swift concertgoer died

Even though it’s still spring in the Southern Hemisphere, temperatures have climbed well above what’s typical even in summer, which is still more than a month away.

The combination of a stagnant area of high pressure, El Niño and human-caused climate change have converged to generate this excessive heat.

Rio has seen a suffocating combination of heat and humidity for days. On Friday, when the woman died at the Taylor Swift concert, midday temperatures crossed the century mark and dew points, a measure of humidity, were in the upper 70s. Any dew point over 75 degrees is oppressively humid.

At a dew point of 77, approximately 23 grams of water are present in every cubic meter of atmosphere, or about 1.55 tablespoons. That’s the weight of roughly nine pennies.

Heat indexes on Friday — a measure of how it feels factoring in humidity — exceeded 120 degrees. Climate historian Maximiliano Herrera tweeted the heat index reached as high as 137 degrees in Rio’s suburbs Saturday.

The higher the heat index, the less sweat the air can evaporate off our bodies. That’s because the air is already closer to its moisture-storing capacity. At high heat indexes, less heat can evaporate from our skin and cool us down as a result. That can lead to difficulties in regulating our body temperatures. If left unchecked, heat exhaustion and heat stroke can occur.

Saturday’s temperatures around Rio were both dangerously high and record-setting. Rio’s Jacarepaguá — Roberto Marinho Airport reported a heat index of 131 degrees on Saturday morning, the product of a temperature nearing 97 degrees and a dew point of 86. Most of the city’s other airports saw high temperatures between 105 and 107 degrees.

According to Herrera, the town of Seropédica, a suburb about 25 miles west-northwest of Rio and 15 miles inland, hit 108.7 degrees, a November record.

Record-high temperatures also spread into Peru and Bolivia. On Saturday, highs of 102.6 in Tingo de Ponaza, Peru and 102.2 degrees in Cobija, Bolivia set November records, according to Herrera.

The heat first moved into Brazil about a week ago. The BBC reported that red alerts were issued for nearly 3,000 towns and cities because of “unbearable” heat. On Nov. 12, it said, Rio hit 108.5 degrees, a record for the month.

The intensity of the heat is forecast to ease some after Sunday but, on balance, temperatures are predicted to remain warmer than normal through the next week in central South America.

What’s driving the heat

Contributing to the heat has been counterclockwise-spinning surface high pressure system just offshore of Brazil. That’s induced warm, humid northerly winds, pumping in the same kind of humidity characteristic of the Amazon rainforest. There’s also a “heat dome,” or ridge of hot, sinking air at higher altitudes. While deflecting away the jet stream and any inclement weather and cloud cover, it’s promoting hot sunshine.

What drought in the Amazon means for the planet

The heat is also being boosted by a strengthening El Niño, the climate pattern associated with warmer-than-normal ocean waters in the tropical Pacific Ocean.

Furthermore, the frequency, intensity and duration of extreme heat events, like this one, are increasing because of human-caused climate change. The planet just observed its warmest 12-month period on record and the last five months have all been the warmest observed.

According to the United Nations, Brazil has warmed by 0.9 degrees during just the past few decades. Land use changes, including deforestation of the Amazon, is expected to accelerate that pace of warming.