A strong polar air mass is bringing Brazil's first intense cold wave of 2026 to the South, Southeast, and parts of the North [1].

The weather event is significant because it creates a sharp temperature anomaly during a period of high social activity, specifically coinciding with Mother's Day celebrations on May 10 [2].

The cold wave began on May 8 and is expected to last until May 13 [1]. This movement of polar air northward is causing temperatures to drop between five and seven degrees Celsius below historic averages in the affected regions [1, 3].

Impacts are most pronounced in the southern states and Mato Grosso do Sul [1, 2]. In Curitiba, the minimum temperature is forecast to reach nine degrees Celsius [1]. São Paulo is also seeing a decline, with a forecast minimum of 14 degrees Celsius [1].

While the South and Southeast face the most direct impact, the polar mass is also causing occasional temperature drops in parts of the North [1, 3]. This wide geographic reach marks the first major thermal anomaly of the year for these regions [3].

Public health officials previously advised residents to prepare for winter conditions to mitigate health risks associated with sudden temperature drops [4]. The current system represents the first realization of those warnings for the 2026 season.

“Temperatures are dropping between five and seven degrees Celsius below historic averages.”

The arrival of a polar air mass this early in May suggests a volatile start to the 2026 winter season. Because the temperature drop is significantly below the historic average, it may put sudden pressure on energy grids and public health infrastructure in urban centers like São Paulo and Curitiba that are not yet fully transitioned to winter protocols.