South America Rainfall Report

Climate Impact Company Early AG Market ALERT

Issued: Friday October 9, 2026

Highlight: South America rainfall report.

Fig. 1-2: CMC ENS and Graph Cast day 1-15 forecast rainfall bias.

Discussion: The least biased 15-day rainfall forecast for South America is the CMC ENS amongst operational models and Graph Cast considering all AI outlooks (Fig. 1-2). The CMC ENS has the smallest wet bias in Southeast Brazil of all the operational models while Graph Cast has shown a dry bias for this zone. Both models indicate a slight dry bias in Central Brazil. The rainfall bias is slight by both models in Argentina.

During the past 7 days, expected wet weather across the southern half of Brazil has developed (Fig. 3) while wet soil moisture conditions in Argentina have expanded northward (Fig. 4).

Utilizing CMC ENS and Graph Cast, the 15-day rainfall anomaly forecasts (Fig. 5-6) indicate wet weather in Southeast Brazil across and east of Paraguay. The Graph Cast is least wet in aerial coverage. CMC ENS is dry across the northwest quarter of Brazil while Graph Cast is dry across most of the northern half of Brazil. Both models shift drier across Northeast Argentina.

In the 16-30-day period, Graph Cast and ECM “weeklies” are similar with wet forecasts maintained for Southeast Brazil (Fig. 7-8). Central and northern Brazil are dry. Wet weather is expanding in Argentina.

Fig. 3-4: Percent normal rainfall observed during the past 7 days and daily soil moisture anomalies analysis across South America.

Fig. 5-6: CMC ENS and Graph Cast 15-day rainfall anomaly forecasts across South America.

Fig. 7-8: Graph Cast and ECM 16-30-day rainfall anomaly forecasts across South America.