Unprecedented Heat Grips São Paulo
São Paulo, Brazil, has recently endured a historic heatwave, with temperatures soaring to record highs for December 2025. The intense heat prompted widespread alerts across several Brazilian states, significantly impacting daily life and public services. Following this period of extreme heat, forecasts indicate a shift towards strong rainfall, a typical characteristic of the region's summer months.
Record Temperatures and Widespread Alerts
The city of São Paulo registered an unprecedented temperature of 35.9°C on Thursday, December 25, 2025, marking the highest December temperature recorded in the last 60 years, according to data from the Mirante de Santana weather station. This record was subsequently broken on Friday, December 26, when the mercury climbed further to 36.2°C. The National Institute of Meteorology (Inmet) responded by issuing a high-risk red alert for the heatwave, which remained in effect until December 29. This alert encompassed not only São Paulo but also extended to parts of Rio de Janeiro, Minas Gerais, Espírito Santo, Goiás, Mato Grosso do Sul, Paraná, and Santa Catarina, affecting millions across southeastern Brazil.
Impacts on Public Health and Resources
The prolonged heatwave, driven by a mass of hot, humid air and an atmospheric block preventing the advance of cold fronts, led to significant concerns for public health. Relative humidity levels hovered between 30% and 45%, exacerbating health risks, particularly for vulnerable populations such as children and the elderly. In a related event, nearly 1,000 people in Rio de Janeiro sought medical attention for heat-related complications over Christmas Eve and Christmas Day. The extreme conditions also strained essential services, with some areas of São Paulo experiencing a surge in water demand of up to 60%, prompting an urgent appeal from the state government to reduce water consumption.
Transition to Rainfall and Storm Alerts
As the historic heatwave began to subside, São Paulo prepared for a transition to more typical December weather patterns, characterized by significant rainfall. Historically, December in São Paulo is part of the rainy season, averaging around 195 mm of precipitation over approximately 24 days. Following the peak of the heat, a yellow alert for storms was issued for São Paulo on December 27. Weather forecasts for the days immediately following the heatwave, from December 28 to December 31, 2025, indicated a high chance of various forms of precipitation, including light rain, heavy thunderstorms, and scattered thunderstorms, providing a much-needed respite from the intense heat.
5 Comments
Donatello
The data is clear: 36.2°C in December is a catastrophe in the making. Wake up, world!
Raphael
While the record heat is definitely alarming and points to broader climate trends, the expected heavy rainfall shows the region's complex, often extreme, weather patterns.
lettlelenok
While the article correctly identifies a record-breaking heat event, the fact that such heat is followed by anticipated heavy rains also underscores the intense, cyclical nature of South American weather.
Comandante
São Paulo's suffering is a stark warning. This isn't normal weather; it's our future without action.
Bella Ciao
The immediate strain on public health and water resources is critical, yet we should also consider how urban development might exacerbate heat island effects alongside global warming.