Trader consensus centers on 16–18°C outcomes for São Paulo’s July 13 maximum because short-range ensemble guidance from INMET and global models indicates a cooler winter day under high pressure and reduced insolation, pulling the expected peak below the 21–23°C July climatological average. Recent observations show overnight lows near 10–12°C with limited daytime warming expected amid possible increased cloudiness or a modest cold-air advection pattern. One-degree resolution hinges on afternoon boundary-layer mixing and exact timing of any weak frontal passage, with model spread reflected in the tight clustering of implied probabilities across the 16–18°C brackets. Official station data from Guarulhos will resolve the market once the daily maximum is recorded.