A polar air mass and cold front are bringing intense cold to southern Brazil and triggering rain alerts for Rio de Janeiro [1].

These weather patterns disrupt regional stability by causing extreme temperature drops and increasing the risk of flooding in densely populated urban centers. The sudden shift in climate poses risks to agriculture in the south and infrastructure in the southeast.

The weather event peaked during the week of May 12, 2026 [3]. During this period, temperatures dropped below 0°C in the states of Santa Catarina and Rio Grande do Sul [1]. This intense cold wave was driven by a strong polar air mass moving across the center-south of the country [4].

In the southeast, the cold front brought a mix of cooling and precipitation. In parts of São Paulo, Rio de Janeiro, and Minas Gerais, minimum temperatures reached 10°C, while maximums hovered around 20°C [2].

While some reports focus on rain in Minas Gerais and Espírito Santo, other forecasts specifically warn of rain and thunderstorms in Rio de Janeiro [2]. The variability in these forecasts highlights the volatile nature of the current atmospheric transition as the cold front pushes through the region [1].

Residents in the southern states of Paraná, Santa Catarina, and Rio Grande do Sul remain the most affected by the freezing temperatures [1]. The movement of the air mass continues to influence weather patterns across the broader center-south region [4].

“Temperatures dropped below 0°C in the states of Santa Catarina and Rio Grande do Sul”

The convergence of a polar air mass and a cold front demonstrates the volatility of Brazil's winter transition. When sub-zero temperatures hit the south simultaneously with heavy rain in the southeast, it puts pressure on regional energy grids and emergency services, particularly in Rio de Janeiro where urban flooding is a recurring risk during strong rain alerts.