Atypical and heavy rains in Brazil’s Center-South region have created a temporary operational bottleneck in the biofuel supply chain, causing a sharp, short-term spike in ethanol prices. Despite the region holding robust inventories and anticipating a strong overall harvest, the weather-driven disruption forced sugarcane mills, or *usinas*, to temporarily halt harvesting and processing, demonstrating how climate events can quickly overrule long-term supply fundamentals.