South America Calling

Late Start to Central Brazil Rainy Season

John Baranick
By  John Baranick , DTN Meteorologist
The central Brazil wet season is expected to start during the Oct. 10-11 weekend, about two weeks later than the 30-year average. (DTN graphic)

The long-awaited start to the central Brazil rainy season is expected during the weekend of Oct. 10-11. This would be about two weeks late; the 30-year average date of the onset of the rainy season in this region is Sept. 26. The dry season has been extensive and longer than normal. Heat and dryness during the last few months have put both topsoil and subsoil moisture at a minimum.

During the next week, a front currently over northern Argentina and southern Brazil will move northward into Mato Grosso and surrounding areas. The front appears to stall, allowing periods of showers and thunderstorms to develop well into the week of Oct. 11-17.

Rainfall amounts of 30-50 millimeters (about 1-2 inches) are forecast with locally heavier amounts. This would be the start of the wet season rainfall.

It has been a rough two weeks on area producers. The lack of soil moisture has limited producers' planting progress; reports indicate soybean planting is only 1.5% finished as of Oct. 4 compared with an average of 4.5%. Good seed-to-soil contact cannot be made with soil moisture below 10% of capacity, which is being estimated by satellite observations. La Nina has been to blame; the prolonged dryness is a typical symptom that occurs in Brazil when sea surface temperatures in the equatorial Pacific are much cooler than normal.

Looking farther ahead, the later start to soybean planting in central Brazil may have a follow-on effect for the winter crops (safrinha). La Nina also has a tendency to shorten the wet season and bring the dry season early. With the already late start, a shortened wet season could put safrinha corn and cotton more at risk.

If the rains end too early, both corn and cotton could be in their reproductive stages when heat and dryness return. This prospect will keep concern for the total Brazil crop weather scenario prominent well into the second quarter of 2021.

John Baranick can be reached at


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