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Climate Impact Company Week 2-to-4 South America Outlook
Issued: Wednesday December 10, 2025
Headline: Deluge of rain in Brazil to finish the year; New Year much drier. Wet to dry Brazil shift catalyst is transient Madden Julian oscillation.
Charts of the day:
Discussion: The wet weather pattern has shifted to Brazil during early December. Heavy rain was observed across Northern Chile to northwestern Argentina during the past week. The 10-day outlook equally combining GFS and ECM reveals wet weather shifts to Paraguay and eastward. Recently developed dryness in Argentina continues.
Week-2 Valid December 21-28, 2025: Soaking rains across much of Brazil.
Discussion: Combining GFS and ECM to project the week-2 outlook yields widespread rains across Brazil, heaviest Northeast. Wet weather also appears in Bolivia, Northeast Argentina, and Uruguay. Wet weather suppresses heat risk in Brazil while Central Argentina is the anomalous dry and hot spot.
Week-3 Valid December 28, 2025-January 4, 2026: Drier shift Brazil.
Discussion: Brazil shifts drier although remaining near normal temperature into the New Year. Argentina is normally wet.
Week-4 Valid January 4-11, 2026: Mostly drier than normal Brazil.
Discussion: Drier pattern continues in Brazil toward mid-January.