**Trader consensus has coalesced around a 16°C minimum for São Paulo on September 9, reflecting verified station observations from the Instituto Nacional de Meteorologia (Inmet) network.** A cold front that brought record-low readings earlier in the month (including 10.1°C on September 7) continued to influence conditions, with clear skies and light winds overnight allowing efficient radiational cooling to that precise threshold before daytime warming resumed. Model consensus and real-time METAR reports aligned closely with this outcome, consistent with September climatology for the region where minima typically range 12–16°C. The overwhelming market-implied probability leaves little room for revision unless post-event quality control adjusts the official reading or a secondary station reports a meaningfully different value.