The reprieve will be brief—another cold front arrives Sunday
Brazil finds itself caught between two cold worlds this week — a polar air mass that drove temperatures to record lows in Santa Catarina is retreating toward the sea, yet a second surge is already forming on the horizon for Sunday. In the south, frost and bitter mornings are giving way to cautious afternoon warmth, while in the northeast, the threat is not cold but water — heavy rains and the specter of floods pressing down on coastal cities. The country's vast geography is, as ever, writing several weather stories at once, each with its own human weight.
- Santa Catarina recorded -5.6°C this year — Brazil's coldest point so far — as a high-pressure system locked in frost across three southern states.
- Wednesday still bites: frost lingers in highland interiors, humidity crashes below 30% in parts of the south, raising fire and respiratory health concerns.
- A second polar front is already en route, set to strike Sunday across the south and central-west with renewed frost, offering little time to recover.
- The northeast faces the opposite extreme — 100 to 150mm of rain forecast between May 12–17, with João Pessoa, Recife, São Luís, and Fortaleza on high flood and landslide alert.
- The country's center and north navigate their own rhythms: the Center-West holds mostly stable, while Amazonian states brace for heavy afternoon thunderstorms.
Brazil's most intense polar cold snap of the year is slowly loosening its grip, but the relief will be short-lived. The air mass that sent São Joaquim, Santa Catarina, to minus 5.6 degrees Celsius — the coldest reading in the country this year — is drifting eastward toward the ocean, allowing afternoons across the center-south to warm incrementally through the week. Still, Wednesday mornings remain sharp, with frost expected in mountain and inland zones, and humidity in parts of the south dropping dangerously low.
The Southeast is catching the cold's final breath. São Paulo, southern Minas Gerais, and southern Rio de Janeiro face frigid mornings before temperatures climb more noticeably during the day. Isolated showers are expected in parts of Minas Gerais, particularly in the afternoon across its southern and central zones.
But the reprieve is already being measured. A second polar front, less severe than the current one but still capable of driving sharp temperature drops, is forecast to arrive Sunday. The southern states and portions of the central-west — including Acre and Rondônia — will fall back into its path, with frost likely returning to the region.
Meanwhile, the northeast is living through an entirely different emergency. A band of heavy rainfall stretching from Rio Grande do Norte to Sergipe, fed by ocean circulation and the advancing Intertropical Convergence Zone, is forecast to deliver 100 to 150 millimeters of rain between May 12 and 17. João Pessoa, Recife, São Luís, and Fortaleza are all under alert, with flooding, inundation, and landslides among the risks authorities are watching closely.
Across the north, Amazonas, Pará, and Roraima continue to simmer under heat and moisture, with afternoon thunderstorms and the potential for severe accumulations. The Center-West remains largely calm, though the far north of Mato Grosso should expect heavier rain near the Pará border. Brazil's climate, as vast as the country itself, is writing several urgent stories at once.
Brazil's grip of polar cold is loosening this week, but the reprieve will be brief. The frigid air mass that has kept temperatures plummeting across the country's southern reaches is gradually retreating toward the ocean, allowing afternoons to warm incrementally through Wednesday and beyond. Yet forecasters are already tracking a second polar surge set to arrive Sunday, bringing another round of sharp temperature drops to the south and central regions.
The current cold snap has been relentless. On Tuesday, São Joaquim in the mountains of Santa Catarina recorded minus 5.6 degrees Celsius—the coldest temperature measured anywhere in Brazil so far this year. That same system has blanketed the southern states with frost, turning mornings in Rio Grande do Sul, Santa Catarina, and Paraná into crystalline, dangerous stretches. The phenomenon is tied to a high-pressure system that has locked in clear skies and intense overnight cooling, especially in elevated and inland areas.
Wednesday morning will still carry that bite. Frost remains likely across mountain regions and the interior south, with minimum temperatures hovering near 1 degree Celsius in many highland and inland spots. Humidity levels have also plummeted in parts of interior Santa Catarina, northeastern Rio Grande do Sul, and southern Paraná, dipping to or below 30 percent—a concern for fire risk and respiratory health. But as the day progresses, the polar air begins its slow eastward drift. The center-south will see gradual warming through the afternoons as the week advances.
The Southeast is also feeling the cold's final exhale. São Paulo, southern Minas Gerais, and southern Rio de Janeiro will experience frigid mornings, though daytime temperatures will climb more noticeably than they have in recent days. Isolated light rain is expected in parts of Minas Gerais, with moderate showers possible in the afternoon across the state's southern, southwestern, and central zones. Low humidity remains a secondary concern in the north of Minas and the interior of São Paulo.
Meanwhile, the north and northeast face an entirely different crisis. Heavy rainfall is intensifying across the region, with storm risks concentrated between Rio Grande do Norte and Sergipe, where ocean circulation and atmospheric conditions are fueling instability. The coastal south of Bahia is also under threat. As the day progresses, downpours are forecast to strengthen across western and northern Maranhão, Piauí, Ceará, Rio Grande do Norte, Paraíba, eastern Pernambuco, Alagoas, Sergipe, and Bahia's coast. João Pessoa and Recife remain on high alert. Between May 12 and 17, rainfall totals of 100 to 150 millimeters are expected in these areas—enough to trigger flooding, inundation, and landslides. São Luís and Fortaleza are also under close watch as the Intertropical Convergence Zone advances northward.
The Center-West will remain largely stable through the week, though the far north and northwest of Mato Grosso should expect moderate to heavy rain near the Pará border. Temperatures will dip in early morning hours across Mato Grosso do Sul and southern Mato Grosso, then rebound during afternoons. The North continues to simmer under heat and moisture, with Amazonas, Pará, and Roraima bracing for afternoon thunderstorms and the risk of severe weather. Accumulations could be substantial across southern Roraima, the Amapá coast, and the Amazonas interior. Acre and Rondônia, by contrast, should see clearer conditions—though the incoming polar mass Sunday may bring temperature drops to those western states.
When the next polar air mass arrives Sunday, it will be less intense than the current system but still potent enough to drive temperatures sharply downward. Rio Grande do Sul, Santa Catarina, Paraná, and portions of Mato Grosso do Sul and Mato Grosso will be in its path, along with Acre and Rondônia. Frost will likely return to southern regions. The cycle of cold and warm, rain and clear skies, will continue its rhythm across a vast and climatically diverse nation.
Citações Notáveis
The current polar air mass is gradually retreating toward the ocean, allowing gradual temperature elevation in the center-south through the week— Weather forecast analysis
The next polar mass should reach Rio Grande do Sul, Santa Catarina, Paraná, and areas of Mato Grosso do Sul, Mato Grosso, Acre, and Rondônia, though it will be less intense than the current system— Forecast outlook
A Conversa do Hearth Outra perspectiva sobre a história
Why does a second cold front arrive so quickly after the first one weakens? Is this unusual?
It's not unusual in May. These polar systems move in waves, especially as the Southern Hemisphere transitions toward winter. One system retreats, but the atmospheric pattern that allowed it to form is still in place, so another follows within days.
The source mentions humidity dropping below 30 percent in parts of the south. Why is that dangerous?
Low humidity accelerates evaporation and dries out vegetation and soil. It increases wildfire risk dramatically and can cause respiratory problems, especially for children and the elderly. It's a secondary hazard that often gets overlooked.
The northeast is facing 100 to 150 millimeters of rain in five days. How does that compare to normal May rainfall?
May is already a wet month in the northeast, but that concentration in such a short window—especially with the geography of those cities—creates acute flooding risk. João Pessoa and Recife sit in low-lying areas with limited drainage capacity.
Will the second polar mass affect the northeast's rain situation?
No, they're separate systems. The cold front will push south and west. The northeast's problem is the Intertropical Convergence Zone, which is independent of polar air. Both regions face different weather crises simultaneously.
What happens after Sunday's cold front passes?
That depends on what atmospheric pattern emerges. These events typically last three to five days before the air warms again. But the source doesn't forecast beyond that, so we're in the unknown.