Widespread thunderstorm activity and abundant tropical moisture forecast for September 22 are the main drivers keeping Miami's daily maximum temperature uncertain across a wide range. Official NWS guidance and model consensus point to highs in the mid-to-upper 80s amid 70-90% chances of showers and storms, with sea-breeze convergence and afternoon convection likely limiting peak heating depending on exact timing and coverage. These variables—cloud thickness, rainfall duration, and wind shifts—create the spread across market bins, as even modest differences in convective onset can shift the observed high by several degrees. Late-September climatology favors 87-89°F under clearer conditions, but persistent moisture this week has already suppressed recent maxima. Updated NOAA model runs and NWS briefings over the next 48 hours will provide the key signals for resolution.