A significant shift in weather patterns is expected across the Center-South region of Brazil this week. A cold front is forecasted to bring widespread rainfall, followed by a sharp decline in temperatures as a cold air mass moves in.
Satellite imagery from NOAA/NASA’s GOES-19 captured the front over Central Argentina and Uruguay late Saturday, May 16. While the system showed low activity with limited rainfall volumes at that time, it is now advancing northward.
Regional Rainfall Forecast
In Rio Grande do Sul, the weather is expected to change this Sunday, May 17, with cloudy to overcast skies covering most of the state. Rain and drizzle are likely, with the highest instability indicated for the northern half of the state, though some areas in the south and west may not see precipitation.
As the front continues its northward progression, rainfall is likely to reach Santa Catarina, Paraná and São Paulo early this week. The system may reinforce existing instability caused by a low-pressure area, which could result in heavy rain and high volumes, particularly in Paraná.
Severe Temperature Drops and Frost
A cold air mass is expected to enter Southern Brazil between Sunday, May 17, and Monday, May 18. This movement is likely to trigger a steep drop in temperatures, leading to a sequence of days with marks significantly below average.
For residents of Rio Grande do Sul, this progression could extend the current period of low temperatures, potentially marking two consecutive weeks of winter-like conditions.
Critical Cold Windows
While cold weather will be present early in the week—especially in the south and west—the most intense cold is expected during the early mornings of Tuesday, Wednesday, and Thursday. During these windows, temperatures may drop more generally across the region.
Much of the interior could see minimums between 0°C and 5°C. Some regions, including the Campanha and Serra do Sudeste, may experience negative temperatures. Specifically, the baixadas of the Planalto Médio (Soledade) and Campos de Cima da Serra could record lows between -3°C and -4°C.
Impact on Porto Alegre
Porto Alegre is expected to face a series of mornings with single-digit minimums. Urban areas may see temperatures around 7°C, while the green belt to the south and east could drop below 5°C. In rural areas of the metropolitan region, minimums could range from 2°C to 4°C.
Frost is likely to occur on nearly every day of the coming week, potentially ranging from moderate to strong. In cities at higher altitudes, actual freezing may occur.
Frequently Asked Questions
Which states are expected to receive rain early this week?
Rain is expected in Rio Grande do Sul, Santa Catarina, Paraná, and São Paulo.
When will the coldest mornings occur in Rio Grande do Sul?
The lowest minimum temperatures are expected during the early mornings of Tuesday, Wednesday, and Thursday.
What are the lowest predicted temperatures for the region?
Some areas, such as the baixadas of the Planalto Médio (Soledade) and Campos de Cima da Serra, could see temperatures as low as -3°C to -4°C.
How does your region typically prepare for a sudden drop to sub-zero temperatures?
