South America Calling

Flooding Rain in Southern Brazil Threatens Harvest, Planting

John Baranick
By  John Baranick , DTN Meteorologist
Heavy, flooding rain in the state of Rio Grande do Sul continues for the next 10 days. (DTN graphic)

A lot of the recent concern in Brazil has been the early end to wet season showers in central Brazil, which is forcing the crop to use up its limited subsoil moisture in a more accelerated fashion.

But to the south, in the state of Rio Grande do Sul, the opposite has been the problem. Heavy, flooding rain has added up to more than 500 millimeters (19 inches) over the last month in some areas, and most have seen more than 300 millimeters (just shy of 12 inches). A large portion of that came in one burst on May 1, a day in which heavy rain totaled 125-250 millimeters (about 5-10 inches) across northern areas of the state.

A stalled frontal boundary that has been waffling around the region has been the cause of the most recent rainfall over the last week or so and it's not done yet. Forecasts have the front continuing over the northern half of the state through May 4. Another 100-200 millimeters (about 4-8 inches) is forecast through that timeframe, with stripes of heavier amounts as well continuing to overflow river basins and cause flash flooding and mudslides.

The front drops southward into northern Argentina and Uruguay for early next week, but then rebounds back into the state for May 8-10 before it likely leaves. The American GFS model has that front sticking around longer, however. In that second burst of showers, another 50-100 millimeters (about 2-4 inches) is forecast. Some areas of the state may end up close to a full meter (39.4 inches) of rainfall over a 30-day period when the front finally passes.

Extensive flooding has already caused the deaths of at least 10 people, with another 21 still missing as of this report from Reuters:…. Property damage is not in question and the governor of the state, Eduardo Leite, has called on Brazilian President Lula for as much aid as can be afforded. Leite describes the flooding situation as the worst in the state's history.

Corn and soybean crops, which are in the midst of harvest, are facing undoubtedly tough conditions. Mostly mature, about 17% of corn and 40% of soybeans are still out in the fields through April 28, according to the most recent CONAB report. That is still a lot of the crop that is in danger from flood damage, delayed harvest, and quality concerns. Winter wheat and other small grain planting should also be starting up, but that will be on hold for the foreseeable future as well.

All this heavy rain comes after significant floods caused issues during the first half of the 2023-2024 growing season. Flooding was a regular topic of conversation as late as January. Portions of the corn and soybean crop were planted late or had to be replanted due to flood damage. Now, the end of their season is coming with the same issues.

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