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Santa Catarina woke up to negative temperatures and frost this Tuesday (28), with a minimum of minus 3.3°C in São Joaquim in the Santa Catarina Mountains, minus 2.2°C in Urupema, and minus 1.8°C in Bom Jardim, the lowest marks of the year caused by a polar cold air mass that also dropped thermometers in Rio Grande do Sul.
Santa Catarina recorded the most intense negative temperatures of 2026 this Tuesday (28), and those who woke up in the Santa Catarina Mountains found fields, fences, and vegetation completely covered by a layer of white frost that transformed the landscape. The state’s minimum was recorded in São Joaquim, where thermometers marked minus 3.3°C according to the state Civil Defense, while Urupema registered minus 2.2°C and Bom Jardim reached minus 1.8°C, negative temperatures that had not occurred in the state since last winter and were surprising for happening still in April, a month that normally marks the transition between the residual heat of summer and the first signs of autumnal cold. The cause of the abrupt drop is a polar cold air mass that advanced over Southern Brazil in recent hours and dropped thermometers throughout the region.
The extreme cold was not restricted to Santa Catarina. In Rio Grande do Sul, Santana do Livramento recorded minus 0.3°C in the Western Border region, Soledade marked 0.4°C, and São Francisco de Paula and Quaraí reached 1°C, with frost recorded in the fields of São José dos Ausentes, which woke up covered in ice. The Civil Defense of Santa Catarina explains that this condition is common in autumn, a transitional season that presents characteristics of both summer and winter, but the intensity of this Tuesday’s negative temperatures indicates that the polar mass that hit the region was particularly strong for this time of year.
Why negative temperatures were so intense in the Santa Catarina Mountains
The Santa Catarina Mountains gather geographical conditions that make it the coldest region in Southern Brazil outside the winter period. São Joaquim, Urupema, and Bom Jardim are located at altitudes exceeding one thousand meters above sea level, an elevation that in itself already reduces the temperature compared to lower areas of the state and, when combined with the arrival of a polar air mass, creates an environment where negative temperatures easily settle during clear, windless dawns.
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Nocturnal radiation, the process by which heat accumulated in the soil during the day escapes into the atmosphere, is more intense on clear and dry nights like the one that preceded this Tuesday’s frost.
Frost formation is a direct consequence of negative temperatures at ground level. When the air near the surface reaches freezing point, the present humidity deposits on grass, leaves, fences, and any exposed object in the form of ice crystals that create the characteristic white layer that covered the Santa Catarina Mountains this morning.
In São Joaquim, the frost was recorded by the Municipal Civil Defense with images showing entirely white fields, a scenario that attracts tourists but represents a real concern for rural producers whose cold-sensitive crops can suffer damage from prolonged exposure to negative temperatures.
How cold it was in Florianópolis and the rest of Santa Catarina
The intense cold of the Mountains was not reproduced with the same severity on the Santa Catarina coast. In the capital Florianópolis, the minimum was 13.7°C, a value far from the negative temperatures of the Mountains but accompanied by wind that accentuated the sensation of cold for those who went out into the streets in the early morning hours.
The difference of almost 17 degrees between Florianópolis and São Joaquim on the same day reflects the decisive influence of altitude and distance from the sea: while the coast is softened by the oceanic presence that acts as a thermal regulator, the Mountains are exposed to cold continental air without any natural barrier.
For the rest of Santa Catarina, Tuesday’s negative temperatures represent the initial mark of a period that should maintain moderate cold in the coming days. Civil Defense indicates that until Friday (May 1st) most of the state should record lows between 10°C and 15°C in the early hours of the day, with mild afternoons that will not reproduce the intensity of Tuesday’s cold.
The polar air mass that caused the negative temperatures gradually loses strength as it moves and mixes with the warmer air of the region, a process that gradually raises the thermometers in the following days.
What negative temperatures mean for the region’s agribusiness
The frost that accompanies negative temperatures is a risk factor for agricultural crops that are in the development phase during autumn. In the Serra Catarinense, fruit producers of apples and grapes live with extreme cold as part of the productive cycle, as these crops need cold hours to complete dormancy and ensure productivity in the following harvest, but frost can cause damage to vegetables, pastures, and annual crops that do not tolerate prolonged negative temperatures.
Producers who did not take preventive precautions such as covering seedbeds or nocturnal irrigation to create a thermal protection layer may find losses when evaluating their crops after the frosty dawn.
Cattle raised on pasture in the Serra also feel the impact of negative temperatures. Frost burns the surface of pastures and temporarily reduces the availability of food for herds that depend exclusively on native fields, a situation that requires supplementation with feed or hay until the vegetation recovers.
For the economy of the mountain region, each extreme cold event is an equation that balances tourist benefits (visitors seeking the experience of cold and frost) with agricultural costs that fall on producers who do not control the climate.
What to expect from temperatures in the coming days in Santa Catarina and the South
The trend for the coming days is gradual relief, but without a return to warmth. Tuesday’s negative temperatures should be restricted to this specific event in the Serra, and the lows for the rest of the week indicate positive values between 10°C and 15°C in most of Santa Catarina, with afternoons that can reach 20°C to 25°C depending on the region and cloud cover.
Autumn in Southern Brazil is precisely marked by this alternation between mild days and intense cold snaps that anticipate the winter pattern.
For those planning to visit the Serra Catarinense in the coming months, Tuesday’s negative temperatures are a reminder that the region can experience extreme conditions well before June. São Joaquim and Urupema have already recorded frost in April in previous years, and the forecast of a possible El Niño for the coming months may alter precipitation patterns without necessarily preventing the occurrence of new cold waves caused by polar air masses.
The coldest day of the year usually occurs between June and July, but April’s negative temperatures demonstrate that the Serra does not wait for the official winter calendar to freeze.
And you, do you live in a region that recorded intense cold this Tuesday? Have you ever witnessed frost in the Serra Catarinense? Leave your opinion in the comments.
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