Portuguese 
English 
Spanish 
5 min of reading 
0 comments 
The most intense polar air mass of 2026 enters the South on Sunday night (26) and could generate the coldest day of the year on Tuesday (28), with temperatures between 0°C and 2°C in the mountains, risk of frost in the Gaúcha Campanha, and lows below 10°C even in Porto Alegre.
The most intense cold of the year already has a date to arrive in Southern Brazil. Climatempo predicts that a continental polar air mass will advance towards Rio Grande do Sul starting Sunday evening (26), with the most severe impacts expected for Monday (27) and Tuesday (28), when cold winds from the extreme south of the continent will rapidly drop temperatures and produce early mornings with temperatures close to 0°C in higher altitude areas. Tuesday (28) should mark the lowest minimums of 2026 in several Gaúcho localities, even with sun throughout the day, because the cold air keeps thermometers low, especially between dawn and mid-morning.
The arrival of this cold represents an abrupt turn in Southern Brazil, which had been registering above-average heat and a heavy, stuffy feeling in recent days. The contrast between the recent heat and the approaching polar air, bringing a risk of early frost, will be felt dramatically: in less than 48 hours, regions that recorded maximums above 25°C will start to face minimums close to zero, a change that requires advance preparation from residents, rural producers, and health services in the areas most affected by the cold. Meteorologists indicate that this type of polar advance should occur with greater regularity as autumn progresses, signaling that the winter of 2026 may arrive with above-average vigor.
Where the cold will be most intense and which regions will have 0°C
The distribution of minimum temperatures predicted by Climatempo draws a map of the cold concentrated in the higher altitude areas and plateaus of the South. The Campos de Cima da Serra gaúcha and the Southern Catarinense Plateau are expected to register between 0°C and 2°C, marks that place these regions at the freezing threshold and justify the alert for possible frost formation on Monday and Tuesday mornings. On the border with Uruguay and in the plateau areas of RS, minimums will be between 3°C and 5°C, values that already require heavy clothing and attention to vulnerable populations.
-
Hidden cave under a castle in Wales reveals 120,000 years of history, with fossils of extinct animals, stone tools, and rare clues about ancient humans
-
Brazil launches an autonomous and electric tractor for coffee farming that works 9 hours without fuel or an operator, costs R$ 340 thousand, has 80 horsepower, uses GPS and Starlink, and can allow a single supervisor to control up to five machines on the farm.
-
New York City subway passengers change plans when the weather is severe, and a study shows why heavy rain reduces night trips while extreme cold hardly affects the routine.
-
Metsul warns of an intense extratropical cyclone in the South Atlantic with rain, winds above 100 km/h, and the advance of a cold air mass over Southern Brazil, dropping temperatures to as low as 5°C in Rio Grande do Sul and Santa Catarina.
The central regions and Gaúcho valleys should fluctuate between 5°C and 7°C, while the Metropolitan Region of Porto Alegre may register minimums between 8°C and 10°C. Even with sun during the day, afternoons will be colder than usual for April, with the perceived temperature reduced by the action of winds accompanying the polar air mass. The cold will not be limited to Rio Grande do Sul: Santa Catarina and Paraná will also feel the effects, especially in the mountainous and plateau areas, where conditions for frost are equally favorable.
The risk of frost and what it means for the South
The combination of clear skies during the early morning and low temperatures creates favorable conditions for frost formation, a phenomenon in which air humidity solidifies on surfaces that have lost heat throughout the night. The areas with the highest probability of frost are the Gaúcha Campanha, the Rio Grande do Sul Plateau, and the Gaúcha and Catarinense mountains, regions where altitude and the absence of cloud cover allow the soil to radiate heat quickly and reach freezing temperatures before dawn.
For agriculture, frost in April is an early event that can cause damage to crops sensitive to extreme cold. Producers who still have autumn crops in a vulnerable stage need to evaluate protection measures before the polar air reaches maximum intensity on Tuesday, because the preparation window is short: between the system’s entry on Sunday night and the peak of the cold on Tuesday morning, it’s just over 36 hours. Intense cold also affects livestock, especially young animals and herds kept in open pastures without adequate shelter.
Why the cold arrives so strongly still in April
The intensity of this polar air mass in the middle of April is surprising because the meteorological winter officially only begins in June. However, autumn in Southern Brazil is a transitional season marked by an alternation between warm periods and incursions of cold air of polar origin, and the amplitude of these oscillations determines whether the cold will be moderate or severe. In 2026, the air mass advancing this weekend is classified by Climatempo as the most intense recorded this year so far, an indicator that the atmosphere is already producing events of magnitude typically associated with May or June.
The meteorological explanation lies in the positioning and intensity of the polar anticyclone that pushes cold air northward. When this high-pressure system is particularly robust, cold winds can advance with greater speed and penetration, reaching latitudes that under normal conditions would only be affected weeks later, and the result is this unseasonal cold that transforms the end of April into a preview of winter. For those who thought April would end without climatic surprises, the polar air mass arriving on Sunday is the definitive answer.
What to expect after the most intense cold of 2026 passes
The trend for the rest of the week after Tuesday’s peak is a gradual recovery in temperatures, but without a return to the warmth of previous days. The polar air mass progressively loses strength as it moves north and mixes with warmer air masses, but the pattern of low nighttime temperatures should persist for a few additional days, especially in mountainous areas where altitude delays warming. For the South, the message is that autumn 2026 is proving to be more rigorous than average and that new polar incursions may occur before official winter.
Meteorologists point out that this early cold behavior directly influences the planning for the coming weeks. If intense polar masses are already reaching the South in April, May could bring even more severe events, with the possibility of negative temperatures in the mountains and more widespread frosts than those predicted for this weekend. The cold arriving now is not an exception: it is the first sign of a winter that, according to projections, could be one of the most significant in recent years for the South region of Brazil.
And you, are you already prepared for the most intense cold of the year? Is your city expected to be affected by the polar air mass? Leave your opinion in the comments.
Be the first to react!