Warm Atlantic sea surface temperatures near South Florida limited overnight radiative cooling and sustained high humidity, anchoring Miami’s June 13 low at the observed 78 °F minimum recorded at Miami International Airport by the National Weather Service. Light southeasterly flow and partly cloudy skies aligned with typical mid-June climatology, keeping readings in the upper 70s to low 80s range with no frontal passages or clear-sky conditions to enhance cooling. Traders assigned 100 % implied probability to the 78-79 °F band once model consensus and official guidance confirmed this outcome, reflecting the narrow uncertainty band around historical normals. A realistic challenge would have required an unexpected dry-air intrusion or stronger radiational cooling under clearer skies, neither of which materialized in the final observations.