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An extratropical cyclone beginning to form this Sunday (26) off the coast of Argentina will push cold air from the Falkland Islands region to Southern Brazil, causing three consecutive nights of intense cold between Monday and Wednesday. MetSul predicts lows of 5°C to 10°C in most of Rio Grande do Sul, with values below 5°C in several cities and the possibility of negative temperatures in the Serra region, in addition to winds of up to 90 km/h and a risk of rough seas on the coast.
Southern Brazil is preparing to face the first winter-like cold wave in 2026. An extratropical cyclone forming this Sunday (26) in Eastern Argentina will rapidly intensify over the South Atlantic, with central pressure potentially dropping to 970 hPa on Monday, a value considered very low for mid-latitudes. The system will act as a cold air pump, drawing cold masses from the Falkland Islands and South Georgia region and pushing them in a corridor that advances from South to North until it reaches Rio Grande do Sul, Santa Catarina, and part of Paraná.
The three coldest nights are expected to occur between Monday (27) and Wednesday (29). Lows in most of Rio Grande do Sul are expected to be between 5°C and 10°C, but several cities will record values below 5°C, especially in higher altitude locations. In the Serra do Sudeste, Campos de Cima da Serra, and Southern Santa Catarina Plateau, thermometers may register around 0°C and even negative values. Frost is forecast in several regions of the state and also in part of Santa Catarina, especially on Tuesday and Wednesday mornings.
How the cyclone forms and why it brings so much cold to Brazil
The process begins with a low-pressure area already active off the coast of Patagonia this Saturday (25). During Sunday, this low pressure initiates cyclogenesis off the coast of Buenos Aires province, forming an extratropical cyclone that rapidly gains strength. On Monday, the system intensifies in the open sea with central pressure around 970 hPa, a value indicating a powerful cyclone for the region.
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Maximum alert for the South: an extratropical cyclone puts 24 cities in Rio Grande do Sul in danger this Sunday, with gusts of up to 60 km/h, intense rain, and risk of flooding, fallen trees, and power outages.
The system’s circulation rotates counter-clockwise and pulls cold air from extreme continental latitudes towards the North. The European model projects a “tongue of cold air” extending from the Falkland Islands region to Southern Brazil, bringing temperatures that cause thermometers to drop in a matter of hours. The cold air begins to enter Rio Grande do Sul between Sunday afternoon and night through the West and South of the state, advancing on Monday to the entire Southern Region.
What to expect during the three cold nights between Monday and Wednesday
The sequence of three nights with intense cold is the most impactful aspect of the event for those living in Southern Brazil. On Monday, the cold will be felt mainly in the cities of Western, Central, and Southern Rio Grande do Sul. By the end of the day, temperatures will drop throughout the state. The lowest minimums are expected to occur on Tuesday (28) morning and Wednesday (29) morning.
For Porto Alegre, Tuesday and Wednesday lows are expected to be between 10°C and 11°C at the Jardim Botânico neighborhood reference point, with values of 8°C to 9°C in neighborhoods further South and East of the capital. In the metropolitan region, lows are expected to range between 7°C and 10°C during the coldest nights. Frost will have significant coverage on Tuesday and Wednesday, affecting various regions of the state with the exception of Greater Porto Alegre and the North Coast, where maritime humidity prevents the formation of ice crystals.
Strong winds and the risk of rough seas on the Gaúcho coast
The cyclone doesn’t just bring cold. Winds intensify in the South and the Gaúcha Campanha region late Sunday with gusts of 50 to 70 km/h on Monday, affecting the South and East of the state. In parts of the Southern Coast, gusts can reach 80 km/h and 90 km/h, a speed sufficient to cause tree falls, roof damage, and power outages in several cities.
In open sea, the intensity of the **cyclone** is expected to generate high waves that may cause **rough seas** on the Rio Grande do Sul **coast** throughout the week. **The combination of persistent strong wind and rough seas requires attention from residents of coastal areas**, fishermen, and those working with port activities. MetSul does not rule out that the sea agitation may also affect beaches and structures near the shore, especially on the **Southern** and Central Coast of **Rio Grande do Sul**.
What happens in Argentina and Uruguay before the cold arrives
Before reaching **Brazil**, the **cyclone** causes severe impacts in neighboring countries. **In Argentina, the Atlantic coast of Buenos Aires province is expected to face very strong winds between Sunday and Monday**, with gusts of 80 to 100 km/h and, in some points like Bahia Blanca, exceeding this level. The **rain** should be locally strong to intense, accompanying the gusts for hours on end.
In Uruguay, the wind gains significant strength from **Sunday** afternoon in the departments of Montevideo, Canelones, Maldonado, and Rocha. **Gusts of 70 to 90 km/h, locally stronger, are expected to cause fallen trees and power outages** between late **Sunday** and Monday. The intensity of the system in the two neighboring countries gives a measure of what **Southern** **Brazil** can expect, although the impacts on Brazilian territory should be less than in **Argentina** and Uruguay.
Rain concentrated between Northern Rio Grande do Sul and Paraná
In addition to the **cold** and wind, the **cyclone** will reinforce a frontal system that brings **rain** concentrated between Northern **Rio Grande do Sul** and Paraná, passing through **Santa Catarina**. **It may rain heavily in some cities, and isolated storms** with lightning, hail, and wind gusts **are not ruled out**. The instability is also expected to advance to Mato Grosso do **Sul** this beginning of the week.
The **cold** spell will not be prolonged. **From Wednesday (29) afternoon, temperatures will already start to rise**, and on Thursday, **minimum temperatures** should be higher than on previous days, although the dawn will still hold remnants of cold. For those living in **Southern** **Brazil**, the recommendation is to ensure warm clothes, protect **frost**-sensitive crops, and check structures that may be affected by the winds early in the week.
Are you prepared for three consecutive mornings of intense cold or were you caught by surprise by the forecast? Tell us in the comments how the weather is in your city and if early winter has already arrived where you live.
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