Recent meteorological model consensus points to a narrow range of maximum temperatures around 19–21°C for São Paulo on May 18, reflecting the city’s typical mid-autumn transition under the influence of the South Atlantic subtropical high. This setup brings reduced solar heating, light easterly winds, and moderate humidity that limit daytime warming while allowing efficient nocturnal cooling. Ensemble spreads from global forecasting systems show minor day-to-day adjustments driven by variable cloud cover and urban heat-island effects, keeping the distribution tightly clustered and explaining the market’s closely matched probabilities near 20°C. Updated short-range model runs and observational data over the next 48 hours will refine the exact peak.