A large part of the south-east of the country remains under the effect of a heatwave which has hit this region since the start of the week, causing temperatures to rise to around 40ºC. For this Friday, the National Institute of Meteorology has maintained an alert for the phenomenon, which covers the states of Rio (which reached 40.1ºC this Christmas) and São Paulo, in addition to the south of Minas and Triângulo Mineiro, the extreme south of Espírito Santo, the coast and north of Paraná and the east of Mato Grosso do Sul.
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This alert highlights that the temperature is 5ºC above average for a period of 3 to 5 days — according to the institute, the warning lasts until the end of this Friday afternoon. For Rio, the sun should only give way from Sunday, the day when the rain should also fall. In São Paulo, rain is already falling this weekend, against a backdrop of heat expected to reach 35ºC.
The capital of São Paulo is expected to have sunshine among many clouds and isolated rain showers and thunderstorms this Friday. At Christmas, the city of São Paulo recorded the highest temperature observed in the month of December and the highest in the entire year 2025. This Thursday, thermometers reached 35.9 °C at the Mirante de Santana meteorological station, in the northern zone of the capital of São Paulo, beating the previous heat mark, which had already lasted almost three decades.
The previous December record – 35.6°C – was recorded on December 3, 1998, also at Mirante de Santana, the main station of the National Institute of Meteorology (Inmet) in São Paulo. First, the record was broken at 3 p.m., when the thermometers reached 35.7ºC, then, at 4 p.m., the thermometer rose further and reached 35.9ºC. In 2025, the hottest day in the city was recorded on October 6, with 35.1ºC.
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Further south in the country, however, Inmet’s warning concerns the risk of storms in Santa Catarina and Rio Grande do Sul. The agency warns that the volume of rain in these states could reach 100 mm/day, in addition to the possibility of winds of up to 100 km/h.
Intense rains also hit the northern region of the country and the states of Mato Grosso, Mato Grosso do Sul, Goiás, Maranhão and Piauí. For this range, the risk is valid until the end of this Friday, with also the possibility of intense winds of up to 60 km/h.
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Porto Alegre, Rio Branco (28ºC) and Porto Velho (29ºC) are the only capitals of the country with maximum temperatures below 30ºC for this Friday. In addition to the heat in Rio, temperatures are expected to reach 37ºC in Belém and Campo Grande.
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