The postponement came after the heat index in the city had risen to as high as 59 degrees Celsius (138 Fahrenheit) Friday, Nov. 17 when a 23-year-old fan in the crowd of 60,000 died during the first Eras Tour show in Brazil.
"I'm writing this from my dressing room in the stadium," Swift posted on Instagram. "The decision has been made to postpone tonight's show due to extreme temperatures in Rio."
"The safety and well-being of my fans, fellow performers, and crew has to and always will come first," she added.
Swift could be seen in videos posted to social media from the night before trying to help fans by dispatching aides to pass out water bottles and even throwing one to the audience herself.
"It's with a shattered heart that I say we lost a fan earlier tonight," Swift said in a post on Instagram to her millions of followers. "I can't even tell you how devastated I am by this."
The Rio Health Secretariat reported that Ana Benevides died Friday evening after suffering cardiorespiratory arrest in the Nilton Santos stadium during Swift's concert.
It said efforts to revive the young woman failed and an investigation had been launched. "At this time, the cause of death cannot be determined," the agency said.
Much of central and southeastern Brazil has been suffering an unusually oppressive springtime heat wave.
Fans lashed out at the venue's handling of the heat, saying officials had prevented them from bringing in water.
"The lack of organization yesterday was absurd. What happened to the young woman was a crime due to bad organization. You just don't deny anybody water," said Yasmin Monteiro, 24, who tried to enter the stadium with five liters of water, before the announcement that the night's concert was postponed.
Caio Wesley, a 25-year-old who tried to carry in four liters of water, described organizers' attitude in prohibiting the entry of liquids as "selfish."
"I brought all this water to see how long I can last," he told AFP.
Brazil's Justice Ministry on Saturday published a resolution requiring event organizers to guarantee that fans have access to drinking water.
"It is unacceptable that people suffer, faint, and even die due to lack of access to water," Justice Minister Flavio Dino said.
In her post, Swift said she would not discuss the woman's death from the stage as "I feel overwhelmed by grief when I even try to talk about it."
"I feel this loss deeply and my broken heart goes out to her family and friends," she added. (AFP)