A polar air mass has triggered the first cold wave of 2026 across several regions of Brazil [1, 2].

This weather event marks a significant shift in regional temperatures, impacting millions of residents in the South, Southeast, and Center-South areas. The sudden drop in temperature disrupts typical seasonal patterns and poses challenges for public health and agricultural planning in these regions.

Paula Nobre said the first winter cold wave arrived in the Center-South on Monday, April 23, and was expected to persist until Friday, April 27 [3]. Other reports indicate the influence of this polar mass continued through the end of the month, with effects lasting through April 30 [1, 2].

The Instituto Nacional de Meteorologia (Inmet) said the city of São Paulo could record its lowest temperature of the year on Friday, April 30, when thermometers are expected to reach 7 °C [2]. This represents a sharp decline for the metropolitan region, as the polar air mass pushes deep into the Southeast.

While the cold wave dominated much of the country, weather conditions remained inconsistent in some areas. In Cambará, Paraná, temperatures reached a maximum of 36 °C during the same period [5]. This contrast highlights the volatile nature of the current weather system, where extreme heat and polar cold can exist within the same state.

Reports from Correio24Horas said the arrival of the polar air mass caused a significant temperature drop specifically in the South and certain areas of the Southeast [1]. The system created cold anomalies in three different mountain regions across the country [1].

The shift from high temperatures to near-freezing levels in urban centers like São Paulo often leads to increased pressure on social services and energy grids as residents increase heating usage. The timing of this wave, occurring in late April, aligns with the transition into the Southern Hemisphere's winter season [3].

“The city of São Paulo could record its lowest temperature of the year.”

The arrival of the first polar wave of 2026 underscores the increasing volatility of Brazil's seasonal transitions. The stark contrast between 7 °C in São Paulo and 36 °C in parts of Paraná demonstrates a fragmented climate pattern that can complicate agricultural harvests and public health responses to temperature extremes.