Traders are pricing 25–26°C as the most likely maximum for São Paulo on May 16 because recent warm advection from the northwest has kept daytime readings several degrees above the long-term May average of 23°C. Official guidance from INMET and regional models shows a modest cold front arriving later in the weekend with light rain and cloud cover that could cap afternoon heating, yet current surface observations and ensemble runs still support a peak near 25°C before any cooling sets in. The close spread between 25°C and 26°C reflects uncertainty in exact timing of the front and how much solar radiation reaches the surface under partly cloudy conditions. Historical analogs for mid-May under similar pressure patterns have produced highs in this narrow band, with only small shifts in wind direction or moisture content tipping the outcome by one degree.