Trader consensus on Polymarket reflects substantial uncertainty in the forecast lowest temperature at Miami International Airport on May 18, with implied probabilities evenly spread at 24-26% across bins from 73°F or below to 88-89°F, driven by divergent NOAA GFS and ECMWF model ensembles showing nighttime lows ranging 73-85°F. A persistent upper-ridge pattern has delivered above-normal warmth this week, including observed lows of 78-80°F on May 11-13 versus the mid-May climatological average of 73-75°F, fueled by high sea surface temperatures near 85°F and urban heat island effects limiting radiative cooling. Key differentiators include overnight cloud cover from sea-breeze thunderstorms, which could trap heat and boost lows into the low 80s, versus clearer skies allowing dips to the mid-70s; daily NWS updates and new model runs through May 17 will refine guidance ahead of resolution.