Recent National Weather Service and ensemble forecasts for Miami on September 20 point to afternoon highs in the upper 80s amid scattered to likely thunderstorms, with 70-90% precipitation chances driven by deep tropical moisture and daytime heating. Convective clouds and rain-cooled downdrafts typically cap peak temperatures by reducing solar insolation and enhancing evaporative cooling, though brief pre-storm warming could push readings toward 88-90°F if storms develop later in the afternoon. September climatology shows average highs near 88°F, but model consensus favors modest suppression from widespread convection over drier, clearer conditions that would support 90°F-plus readings. Updated short-range guidance and radar trends over the next 48 hours will clarify storm timing and intensity, key variables separating the tightly bunched 86-91°F market bins.