Recent short-range forecast models from agencies like INMET and international ensembles show maximum temperatures in São Paulo hovering near 18°C on May 19, with limited spread between 17°C and 19°C driven by a passing frontal system and associated cloud cover that is moderating daytime heating. This positions the market’s closely bunched probabilities around the historical May average high of 21–23°C, reflecting genuine uncertainty in how quickly the cooler air mass will clear and allow greater solar warming. Traders are also weighing typical autumn variability, including potential afternoon showers that could cap peaks below 20°C, while any faster clearing or stronger subsidence would favor the upper end of the range. Updated model runs expected within the next 24–48 hours will provide the clearest signal ahead of resolution.