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The extratropical cyclone that acted last week has moved away to the ocean, but the cold front associated with it remains active and pushes polar air to the South, Southeast, and part of the Midwest with minimums between 6°C and 7°C in the mountains already this Friday
If you live in the South of Brazil or in mountainous regions of the Southeast, prepare the thick blanket. An unusually strong cold air mass for April is advancing through the country at this moment and may drop temperatures close to 0°C in the Gaucho and Santa Catarina mountains already this Friday (10).
The phenomenon comes in the wake of the extratropical cyclone that acted over Brazil last week. According to Meteored, the cyclone moved away towards the ocean this Wednesday (8), but the cold front associated with it remains active and is pushing polar air into the continent. It is this combination of persistent cold front with cold air mass that is creating the conditions for the first real cold episode of autumn 2026.
And the most surprising thing is that we are not talking about June or July. We are talking about April.
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Which regions will be most affected?
The strongest impact will be felt in the high-altitude areas of the South of Brazil. According to the forecast published by the Meteored portal this Wednesday (9), the minimum temperatures in the Gaucho and Santa Catarina mountains may reach between 6°C and 7°C already on Friday (10). And considering the deviation of 3 to 4°C that models usually present at specific points, it cannot be ruled out that municipalities like São Joaquim, Urupema, Urubici, and São José dos Ausentes register even lower minimums.
In practice, this means a real risk of temperatures close to 0°C and isolated frosts in the southern mountains, something that normally only happens more frequently starting in May.
But the cold will not be restricted to the South.
Will the Southeast and Midwest also feel it?
Yes. Throughout the weekend, the cold air mass advances towards the Southeast and reaches states like Rio de Janeiro, Espírito Santo, and Minas Gerais between Friday and Sunday (12), according to Meteored. Most of the region should record minimums below 20°C, with colder weather concentrated around the Mantiqueira Mountains.
In this region, which includes municipalities like Campos do Jordão (SP), Monte Verde (MG), and Visconde de Mauá (RJ), there is a possibility of isolated frosts over the weekend, according to the forecast from the ND Mais portal.
Mato Grosso do Sul should also feel the drop, along with the south of Mato Grosso and the east of Goiás, where temperatures will be milder than the norm for the season.
For cities like São Paulo, the change will be noticeable mainly in the early mornings and the first hours of the day, with temperatures dropping to the range of 12°C to 15°C. Nothing extreme, but enough for those who have been experiencing above-average heat to feel the contrast.
Is this cold wave normal for April?
It is uncommon at this intensity. According to meteorologist Estael Sias, interviewed by the ABC+ portal, the first days of intense cold usually occur in the second half of April, especially in the last ten days of the month. The American climate model CFS had already indicated the possibility of lower temperatures in this window, although without consensus among all models.
What makes this episode particular is that it arrives earlier than expected and with enough strength to produce frost, a phenomenon that requires very specific conditions: air temperature below 5°C, clear sky, absence of wind, and low relative humidity. When all this aligns, the dew freezes on surfaces and forms the white layer that characterizes frost.
According to the magazine Exame, for frost to form, it is necessary for the temperature to remain close to 0°C for a sufficient time for the freezing process to occur on exposed surfaces.
What is the difference between this cold air mass and the previous ones in 2026?
There have been other incursions of cold air this year. In January, the first cold air mass dropped temperatures in the South and Southeast, but with minimums that remained in the range of 7°C to 10°C in the mountains. In March, two cold fronts passed through the country causing heavy rains and drops of more than 10°C, but without reaching marks close to zero.
This is the first time in 2026 that models indicate a concrete risk of 0°C and frost in mountainous areas, according to Meteored. It is a clear sign that autumn is truly imposing itself and that the climate pattern is changing phase.
Meteored’s forecast also indicates that, even with the quick passage of this cold air mass, the week will be marked by colder weather than normal throughout the central-southern part of the country. It is the type of change that is first felt in the early mornings, when the thermometer drops, and then in the afternoons, which cease to be hot and become merely mild.
For those who follow the weather, this is the milestone. Autumn 2026 has finally arrived for real.
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