In February 2025, an area of high pressure parked over the southern Atlantic Ocean, causing temperatures to soar in parts of South America. In Brazil, the heat led officials in Rio Grande do Sul to delay the start of school and people in Rio de Janeiro to flock to the beach.

The summer heat wave is depicted on this map, which shows air temperatures modeled at 2 meters (6.5 feet) above the ground on February 17. It was produced by combining satellite observations with temperatures predicted by a version of the GEOS (Goddard Earth Observing System) model, which uses mathematical equations to represent physical processes in the atmosphere. The darkest reds indicate areas where temperatures reached or exceeded 38 degrees Celsius (100 degrees Fahrenheit).

The city of Rio de Janeiro saw especially warm conditions on February 17. According to news reports, a weather station in the Guaratiba neighborhood recorded temperatures of up to 44°C that day(111°F)—the hottest temperature measured since the development of the city’s climate alert system 10 years ago.

Brazil’s National Institute of Meteorology (INMET) noted several other municipalities across the state of Rio de Janeiro where temperatures exceeded 40°C (104°F) on February 17, such as Silva Jardim, which hit 42°C (108°F). The region’s heat wave continued through the week before returning closer to normal as the focus of the heat shifted south into Argentina.

Heat was already evident in northern Argentina on February 17, when the country’s National Weather Service (SMN-Arg) reported highs reaching up to 40°C. As of February 27, SMN-Arg noted that six provinces were under a red-level (very dangerous) alert for extreme heat.

 

NASA Earth Observatory image by Michala Garrison, using GEOS-5 data from the Global Modeling and Assimilation Office. Story by Kathryn Hansen.