Recent UK Met Office and ECMWF ensemble forecasts have converged on a daytime maximum of exactly 18°C for London on May 17 under partly cloudy skies and moderate westerly flow, producing the market’s near-100% pricing on that outcome. These models incorporate current observational data from surface stations and upper-air soundings, showing stable Atlantic air without significant warm advection or clearing that would push temperatures higher. Historical May climatology for the region places average highs near 17–19°C, so today’s conditions align closely with the expected range. The only realistic scenarios that could alter the result involve rapid model revisions from afternoon observations or unexpected insolation increases, though both appear unlikely given the latest guidance.