Forecast consensus from the National Weather Service and other models points to a typical late-September pattern for Miami on September 21, with highs in the upper 80s amid high humidity and a 70-90% chance of afternoon showers and thunderstorms. Persistent moisture, light variable winds shifting southwest, and strong daytime heating favor scattered convection that can limit peak temperatures through cloud cover and evaporative cooling, while any delay in storm development could allow brief pushes toward 90°F. Sea-breeze convergence and the lack of strong steering currents add variability in timing and coverage, keeping exact maxima uncertain across short-range guidance. This genuine forecast spread—rather than any single catalyst—explains the market's tightly clustered implied probabilities across the 76–93°F buckets. Updated model runs and NWS briefings over the next 48 hours will likely refine the range.