April 2025 is set to bring significant changes to Brazil's climate, marking the effective start of autumn with a mix of temperature fluctuations and rainfall patterns. According to Climatempo, a leading meteorology company, the month will witness the influence of polar air masses generating cold fronts, particularly in the Southeast region. As the La Niña phenomenon weakens and nears its end, its impact on Brazil's climate diminishes, paving the way for new weather dynamics.
The South Atlantic, off the coast of the Southeast, is currently warmer than normal, facilitating the formation of low-pressure areas and increasing moisture evaporation. This situation is expected to lead to the formation of rain areas, especially as the month progresses. April typically marks the beginning of a reduction in rainfall across most parts of Brazil, but this year, Climatempo forecasts a slightly below-average total precipitation for most regions, with some areas in the South expecting above-average rainfall.
As the month begins, hot and humid air predominates in the Southeast states, creating instability, particularly in São Paulo. The first cold front is expected to arrive on Thursday, April 3, 2025, bringing an increased risk of heavy rain and advancing through the state into the following day. Heavy rain is anticipated along the coast of São Paulo during the weekend of April 5-6, with a high potential for disruptions.
Looking ahead, the second half of April will see two moderate to strong polar air masses, which will lead to a drop in temperatures and a reduction in the frequency and volume of rainfall. The accumulated rainfall for the month is expected to remain within historical averages for most of São Paulo, with averages ranging between 80 mm to 100 mm in most regions, and up to 140 mm in the extreme west, southwest, and south of the state.
In the South region, the arrival of a new cold front on April 2, 2025, has already prompted alerts for storms and heavy rains, especially in Rio Grande do Sul. This cold front is expected to bring significant instability and a notable drop in temperatures across the southern states. Meteorologists warn that strong rains are likely, with the highest volumes expected in cities like Santa Terezinha de Itaipu (PR), forecasted to receive 43 mm of rain, and Jaguarão (RS), with 35 mm.
As temperatures drop, the South region is likely to experience some of the coldest weather seen in Brazil this year. On April 3, the cold will be most intense in Rio Grande do Sul, but other states, including parts of Minas Gerais, may also feel the chill. Minimum temperatures of 15°C are anticipated in cities like Chuí and Santana do Livramento, while areas like Camanducaia and Dom Pedrito may see lows of 16°C.
Friday, April 4, is expected to bring even colder conditions, particularly in Santa Catarina and Rio Grande do Sul, with Urupema and São Joaquim in Santa Catarina forecasted to hit a chilling 6°C. Similarly, Urubici (SC) and São José dos Ausentes (RS) are expected to experience temperatures around 7°C. The early morning of Saturday, April 5, will continue the trend of cold weather, with the potential for frost and negative temperatures in the higher elevations of the Serra Catarinense.
Despite the arrival of these cold fronts, April is projected to conclude with temperatures remaining above the historical average in most areas of São Paulo, except in the south where temperatures are expected to align more closely with typical averages. The possibility of frost, while low, cannot be entirely ruled out in elevated areas such as Campos do Jordão at the end of the month.
In summary, April 2025 is shaping up to be a month of contrasts for Brazil, with the interplay of warmer ocean temperatures, cold fronts, and varying precipitation patterns. As the country transitions into autumn, residents can expect a mix of weather conditions that may impact daily life and agricultural practices across the regions.
