A polar air mass is bringing the first cold wave of 2026 to central-south Brazil, causing sharp temperature drops and severe weather.

This weather system is significant because it marks the year's most substantial temperature decline, creating risks of frost and storms for millions of residents across several states.

The cold wave began on Friday, May 8 [5], and is expected to persist until Wednesday, May 13 [6]. Meteorological agencies, including INMET, report that the strongest impacts occurred over the weekend of May 9 and 10 [2]. The system is driven by a polar air mass moving northward over South America, which is interacting with existing heat and humidity to trigger the temperature plunge [1, 2].

Impacts are widespread across the central-south region, including Rio Grande do Sul, São Paulo, Minas Gerais, Rio de Janeiro, and Mato Grosso do Sul [1, 3]. In the South, some areas have already recorded temperatures below five °C [4].

Forecasts for major cities indicate a varied impact. Campo Grande is expected to see a minimum temperature of 10 °C [1], while São Paulo is forecast to drop to 13 °C [1]. Rio de Janeiro will experience a milder decline, with a predicted minimum of 21 °C [1].

Meteorologists said the event will cause the greatest temperature drop of the year and bring a risk of frost to hundreds of Brazilian cities [7]. Meteorological agencies said the polar air mass advanced through the interior of South America to provoke this shift [8].

In addition to the cold, the system is bringing strong rains and a risk of storms to the affected regions [3]. The Exame editorial team said the first cold wave of 2026 should cause a strong drop in temperatures across much of the country's central-south region [9].

“The first cold wave of 2026 should cause a strong drop in temperatures across much of the country's central-south region.”

The arrival of a polar air mass this early in May suggests a volatile transition into the southern hemisphere's winter. The combination of extreme cold and heavy precipitation increases the risk of agricultural frost damage and puts pressure on urban infrastructure in cities like São Paulo and Rio de Janeiro, which may not be fully prepared for the year's sharpest temperature decline.