Current National Weather Service and private model guidance for Miami on August 21 points to overnight lows near 80–82 °F, consistent with the market’s near-even split between the 80–81 °F and 82–83 °F bins. Subtropical humidity and scattered convective clouds are limiting nocturnal radiative cooling, while light southeasterly flow and urban heat retention keep minimum temperatures from dropping further. Recent model runs show only modest disagreement on the timing and coverage of any late-day showers, which could enhance or suppress cooling by a degree or two. Historical August climatology for Miami International Airport places the average low at 80 °F, providing a narrow baseline against which traders are weighing the latest forecast updates.