Traders assign closely matched implied probabilities around 35-37% to Miami's lowest temperature on July 19 falling in the 80-85°F range because short-range forecast models show modest uncertainty in overnight cooling. High humidity, weak pressure gradients, and Atlantic sea-surface temperatures near 85°F typically limit radiative cooling in South Florida's tropical climate, while sea breezes and variable cloud cover can shift the minimum by a few degrees. Official National Weather Service guidance and ensemble runs from the GFS and ECMWF currently cluster near the upper 70s to low 80s, with historical July averages around 76°F serving as baseline. Minor differences in predicted wind or precipitation timing remain the key variables that could nudge the outcome before the next model update.