**Persistent warm, humid conditions driven by a tropical air mass and southeast flow are positioning 80-81°F as the leading market outcome for Miami’s lowest temperature on September 5.** Official National Weather Service and model guidance show overnight lows holding in the upper 70s to low 80s amid high dew points near 78–80°F, widespread cloud cover, and scattered thunderstorm activity that limits nighttime radiative cooling. This setup aligns with climatological norms for early September in South Florida, where average lows hover near 76°F but recent patterns have trended warmer due to elevated moisture and weak steering winds. Forecasts from multiple sources converge on a minimum near 78–81°F for the night of September 4–5, with any brief clearing unlikely to produce significant drops. The 24% implied probability on 73°F or below reflects residual uncertainty in exact cloud timing or localized cooling, but current model consensus and the absence of a cooler air mass make such outcomes less probable. Traders are weighting the most recent NWS point forecasts and ensemble guidance, which emphasize stable overnight warmth through the period.