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Simultaneous advance of the two meteorological systems is expected to cause storms, strong winds, and a significant drop in temperature in the states of the South, Southeast, and Midwest in the first days of the month
According to information released by the portal ND Mais, in a report by journalist Carolina Sott published on June 29, 2026, Brazil will start July with a radical change in weather in much of the national territory. A cold front is advancing through the South-Central part of the country, reinforced by an extratropical cyclone, combined with an intense polar air mass. According to the forecast by Meteored, cited by ND Mais, this combination of systems will bring storms, strong winds, and negative temperatures in the coming days.
This triple combination — cold front, extratropical cyclone, and polar air mass acting simultaneously — explains the intensity of the phenomenon. In this sense, although cold fronts are common at this time of year, rarely do the three systems advance so synchronously, which helps justify the reinforced alert for various regions of the country.
Wednesday (July 1st): the beginning of instabilities
The weather change begins to take shape on Wednesday, when new areas of instability reinforce the cold front already active in the South of the country. Rio Grande do Sul, Santa Catarina, and Paraná are on alert for heavy rains and isolated storms.
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At night, the polar air begins to enter the gaucho territory, and the strong wind will increase the feeling of cold in the region. Meanwhile, however, the scenario is quite different in the Southeast and Midwest: in these regions, the weather remains stable, with sun and mild temperatures — a contrast that, according to the forecast, should not last long.
Thursday (July 2nd): cyclone and polar air mass meet
On Thursday, the cold front gains even more strength with the formation of an extratropical cyclone in the ocean, at the height of the Southern Region. The risk of isolated storms continues, moving to the east and north of Santa Catarina and to the east of Paraná during the night.
Furthermore, the cold air will cross borders: after advancing through Brazil, it passes through Argentina and Paraguay until reaching Bolivia. Here, the southern winds cause the phenomenon of cold snap in Rondônia, and still lower temperatures in the west of Mato Grosso and Mato Grosso do Sul. At the end of the night, heavy rain and storms hit the south of São Paulo, on the border with Paraná.
The main highlight of the day, however, is the intense cold recorded during the night. See the temperature forecast by region:
- Serra Gaúcha and Catarinense: thermometers in sharp decline, with a chance of negative temperatures;
- Rio Grande do Sul (other regions): minimums oscillating between 3°C and 7°C, with maximums of at most 13°C in the afternoon;
- Santa Catarina: minimum temperatures ranging between 5°C and 14°C;
- Paraná: thermometers registering minimums between 10°C and 19°C.
Friday (July 3): sharp drop in temperature reaches the Southeast
Friday marks the major weather change for the states of the Southeast, driven by the advance of the cold front along the coast. The day is expected to be cloudy, with light rain in most of the state of São Paulo — except in the western region — and throughout the territory of Rio de Janeiro.
The highlight of the day, however, is the cold: in eastern São Paulo, the maximum temperature may be just 10°C, even in the middle of the afternoon. In the Midwest, the system increases the region’s cloudiness, but according to the forecast, there is no expectation of rain there.
Given this scenario, meteorology agencies reinforce the alert for wind gusts and a sharp drop in temperature throughout the week — making it advisable to reinforce precautions against the cold and follow official updates in the coming days, as systems of this nature may undergo adjustments in intensity and trajectory as they approach.
The combination of an extratropical cyclone and a polar air mass reinforces a pattern that has become familiar to those living in the South and Southeast of Brazil in recent winters: abrupt temperature changes in a few days, alternating between sun and intense cold almost without transition. It remains to be seen whether this will be just another passing cold wave — or if the country is facing a climate pattern that will repeat with increasing frequency in the coming winters.
