Recent atmospheric patterns, including persistent cloud cover and light rain associated with a passing frontal system, are moderating overnight radiative cooling and anchoring trader-implied probabilities tightly around 16–18 °C for São Paulo’s October 6 minimum. Multiple global and regional models currently converge on overnight lows near 17–19 °C, with limited diurnal temperature range expected under humid, overcast conditions that reduce the potential for stronger drops. This narrow clustering reflects genuine forecast uncertainty in boundary-layer moisture and wind speeds rather than a single dominant outcome, while the low odds assigned to 13 °C or below align with climatological baselines showing rare sub-15 °C minima this early in spring. Updated high-resolution model runs and real-time surface observations over the next 48 hours will likely tighten the distribution ahead of market resolution.