A polar air mass moving southward across Brazil brought rain, gusty winds, and a sharp temperature drop to São Paulo on Sunday [1, 2].
The sudden shift in weather disrupted Mother's Day celebrations in the metropolitan area, coinciding with a meteorological phenomenon known as thermal shock [1, 3].
Meteorologists tracked the polar air mass as it crossed the south of Brazil toward the southeast [1]. This system is capable of causing temperatures to fall by 10 °C in a few hours [1]. In São Paulo, the maximum temperature forecast for May 10 was 19 °C [2], though other reports indicated temperatures could drop closer to 10 °C during the event [4].
The cold front brought significant instability to the region. In addition to the rain and wind, minimum temperatures in the area were expected to fall below 10 °C [5]. This represents one of the first intense polar air masses of 2026 to impact the city [4].
Residents experienced a stark contrast between previous warmth and the sudden arrival of winter-like conditions. The system's movement through the southeast is part of a broader weather pattern affecting several Brazilian states, with some areas facing the risk of frost [5].
“A polar air mass moving southward across Brazil brought rain, gusty winds, and a sharp temperature drop to São Paulo.”
The arrival of a polar air mass during early May indicates a rapid transition into the southern hemisphere's winter cycle. The resulting 'thermal shock'—a rapid drop in temperature—can stress urban infrastructure and public health, particularly for vulnerable populations in a city like São Paulo that is not always equipped for sudden, extreme cold.
