Recent forecasts from the National Weather Service and global models indicate Miami’s overnight low on May 21 will likely settle in the mid-to-upper 70s, shaped by warm Atlantic sea-surface temperatures near 80°F, prevailing easterly flow, and scattered convective showers that can enhance radiational cooling. The closely matched market-implied probabilities for 73°F or below versus 78–79°F reflect uncertainty in cloud cover and timing of any weak frontal passage, which historically can drop lows by 2–4°F. Typical mid-May climatology shows overnight minima averaging 74–75°F, with drier subsidence favoring the upper end and thunderstorm outflows favoring the lower end. Updated model runs and local observations over the next 48 hours will clarify whether conditions trend toward the cooler brackets currently favored by traders.