**Persistent tropical moisture and an upper-level low over the region are sustaining scattered thunderstorms and variable cloud cover across South Florida, moderating overnight radiative cooling and keeping Miami's minimum temperatures on September 21 centered in the mid- to upper-70s.** Official National Weather Service guidance and ensemble forecasts indicate lows near 76–78°F under mostly cloudy to overcast skies with southwest winds and precipitable water values remaining elevated above 2 inches. Convective timing and intensity introduce the main uncertainty: stronger afternoon/evening storms could enhance evaporative cooling and nudge readings toward 74–75°F, while partial clearing overnight might allow brief dips near 72–73°F. This setup aligns closely with historical late-September climatology for Miami but features above-average humidity and weak steering flow that limit extremes, explaining the tightly clustered market probabilities across the 72–77°F bins. Updated model runs and NHC/NOAA briefings through the weekend will refine the exact minimum.