Alert for rain and thunderstorms: intense instability marks the transition between April 28 and May 1, with almost daily rain and high humidity, while the South faces storms, lows of 6 °C, risk of frost, and volumes of up to 80 mm.

Written by Alisson Ficher

Published on 27/04/2026 at 20:43

Updated on 27/04/2026 at 20:44

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Instability persists in the North with frequent rain and humid heat, while a cold front changes the pattern in the South with storms and a sharp drop in temperature, forming a striking climatic contrast at the turn of April to May in different regions of Brazil.

Rio Branco and Porto Velho are expected to experience unstable weather at the turn of April to May, with overcast skies, rain at various times, and the possibility of isolated thunderstorms, while Southern Brazil faces storms and a sharper drop in temperatures.

The forecast from the National Institute of Meteorology for the week of April 27 to May 4 indicates a higher concentration of rain in the North and Northeast regions, while a cold front reorganizes the weather in the South and favors the entry of cold air.

Weather forecast in Western Amazonia

In Western Amazonia, the focus is on the capitals of Acre and Rondônia, which appear in a persistent humidity band, even if they are not at the core of the highest accumulated rainfall predicted for the country during the period.

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How rain is distributed in the North Region

Inmet’s weekly bulletin indicates that the largest volumes of rain are expected to occur in areas of Amazonas and Pará, especially near the Negro and Amazon rivers, where accumulations can exceed 100 millimeters in seven days.

In other areas of the North Region, rain appears more irregularly, with volumes generally below 50 millimeters, but still sufficient to maintain pockets of instability at different points along the Amazonian strip.

This pattern helps explain why Rio Branco and Porto Velho draw attention even outside the rainiest areas on the national map, as both cities remain under the influence of heat, humidity, and available water vapor.

For urban routines, the scenario requires attention to commutes, outdoor activities, and rapid changes in the sky, as the forecast indicates isolated showers and thunderstorms, not a uniform episode of rain over several days.

Cold front causes storms and cold weather in the South

While Western Amazonia remains under humid heat, the South of the country undergoes a more abrupt change, caused by the action of a cold front and the subsequent entry of a cold air mass.

According to Inmet, the frontal system favors severe weather in the first days of the week, with storms, intense rain, wind gusts, lightning, and the possibility of hail in areas of Rio Grande do Sul, Santa Catarina, and Paraná.

Accumulations can reach 80 millimeters in seven days in Rio Grande do Sul and Santa Catarina, while Paraná is expected to record volumes of up to 70 millimeters in the same period, according to the weekly forecast.

The difference compared to the North lies in the type of atmospheric change, as in the South, rain is accompanied by a more noticeable drop in temperature and a feeling closer to winter.

Inmet also indicated minimums around 6 °C in south-central Rio Grande do Sul starting Monday, April 27, in addition to favorable conditions for frost formation in more susceptible areas of Rio Grande do Sul and Santa Catarina.

Central Brazil with dry weather and low humidity

Between the Amazonian humidity and the advance of cold in the South, the central strip of Brazil is expected to register a predominance of dry weather, low cloudiness, and little prospect of rain throughout the week.

In the Central-West, the forecast indicates irregular showers only in the northwest of Mato Grosso and the south of Mato Grosso do Sul, with accumulations that can reach 40 millimeters in seven days.

In the Federal District, Goiás, and a good part of Mato Grosso do Sul, the trend is for stability, with reduced chances of light and isolated rain, according to Inmet’s meteorological bulletin.

The turn between April and May, therefore, brings together three distinct scenarios in the country: humid instability in the Western Amazon, dry air in central Brazil, and the advance of cold weather with storms in the South Region.

In this context, Rio Branco and Porto Velho gain relevance by representing the persistence of rain and mugginess in the western Amazon, while municipalities in the South are already feeling the first signs of a colder pattern.

The combination reinforces the typical contrast of the Brazilian autumn, when different air masses act simultaneously and produce very distinct conditions between distant regions of the national territory.

Alert for rain and thunderstorms: intense instability marks the transition between April 28 and May 1, with almost daily rain and high humidity, while the South faces storms, lows of 6 °C, risk of frost, and volumes of up to 80 mm.

Instability persists in the North with frequent rain and humid heat, while a cold front changes the pattern in the South with storms and a sharp drop in temperature, forming a striking climatic contrast at the turn of April to May in different regions of Brazil.

Weather forecast in Western Amazonia

How rain is distributed in the North Region

Cold front causes storms and cold weather in the South

Central Brazil with dry weather and low humidity

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Alert for rain and thunderstorms: intense instability marks the transition between April 28 and May 1, with almost daily rain and high humidity, while the South faces storms, lows of 6 °C, risk of frost, and volumes of up to 80 mm.

Instability persists in the North with frequent rain and humid heat, while a cold front changes the pattern in the South with storms and a sharp drop in temperature, forming a striking climatic contrast at the turn of April to May in different regions of Brazil.

Weather forecast in Western Amazonia

How rain is distributed in the North Region

Cold front causes storms and cold weather in the South

Central Brazil with dry weather and low humidity

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Norway is drilling 27 kilometers of rock 392 meters below the bottom of a fjord to build the world’s largest and deepest underwater road tunnel — when completed, a 21-hour journey will be reduced to 10.

Chinese engineers begin filling a 217-meter dam at an altitude of 3,000 meters and prepare a 2,240 MW hydroelectric power plant to integrate hydropower, solar, and wind energy in the upper Jinsha.

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