Persistent easterly flow and a stalled frontal boundary are driving scattered to likely thunderstorms across Miami on September 17, increasing cloud cover and limiting solar heating that would otherwise push highs into the low 90s. National Weather Service guidance points to upper-80s maxima amid 60-80% rain chances, with model consensus showing afternoon peaks near 86-89°F depending on storm timing and coverage. Elevated humidity and onshore winds further moderate temperatures by enhancing mixing and reducing insolation. The tight clustering of market-implied odds around the 86-91°F bins reflects this forecast uncertainty, where small shifts in convective initiation or intensity could determine whether the daily high settles in the mid- or upper-80s range. Updated short-range model runs and afternoon observations will provide the next key data points for resolution.