High humidity and subtropical maritime air in Miami limit overnight radiative cooling, keeping minimum temperatures near seasonal norms of 78°F amid light winds and warm Gulf Stream waters. Scattered afternoon thunderstorms and associated cloud cover on August 4–5 further trap heat, supporting the market’s near-even split between 78–79°F (49%) and 76–77°F (43.5%). Model guidance shows modest variability in boundary-layer moisture and convective timing that could tip the low a degree either way, while clearer breaks would favor the cooler bin. Traders weigh National Weather Service forecasts against climatological baselines, recognizing that typical August conditions rarely allow deeper drops absent unusual synoptic cooling.