A severe polar air mass drove temperatures to record lows across Brazil's Centro-Sul region in early May 2026 [1, 2].

The event marked the coldest day of the year for several regions, disrupting normal weather patterns and threatening infrastructure across five states [4].

Bom Jardim da Serra in Santa Catarina recorded a low of -9.2 °C [1]. Other reports indicated Santa Catarina reached -7 °C, which was noted as the lowest temperature of the year for the state [2]. Sub-zero temperatures were reported in 69 cities across the region [1].

The cold wave peaked between May 10 and May 12, 2026 [2, 3]. In Paraná, May 10 was recorded as the coldest day of the year [3]. Meteorologists said the cold wave would persist until May 13, 2026 [4].

While the highlands saw extreme freezes, the temperature drop extended into major urban centers. Forecasts for the period included a minimum of 10 °C in Campo Grande, 13 °C in São Paulo, and 21 °C in Rio de Janeiro [8].

This weather phenomenon was driven by a "massa polar," or polar air mass, moving southward [2, 5]. This movement pushed frigid air from the south deep into the Brazilian interior, creating a sharp temperature gradient across the country.

Earlier forecasts had predicted a minimum of -4 °C in the high areas of Santa Catarina [6], though actual recorded temperatures later exceeded those estimates [2].

“Bom Jardim da Serra in Santa Catarina recorded a low of -9.2 °C”

The occurrence of sub-zero temperatures in 69 different cities demonstrates the significant reach of the 2026 polar air mass. When temperatures drop below the initial forecasts—such as the shift from a predicted -4 °C to a recorded -9.2 °C—it indicates an unusually strong atmospheric push that can strain energy grids and impact agricultural yields in the Centro-Sul region.