Recent numerical weather prediction models from the Met Office and ECMWF indicate a changeable pattern over southern England through May 20, with low pressure to the north favoring variable winds that could either advect milder Atlantic air or draw cooler northerly flow. This drives the market's broad distribution, where traders assign 34% implied probability to a minimum of 17°C or higher reflecting potential for limited overnight cooling under cloud cover, while 20.5% on 7°C or below accounts for clear-sky radiative losses if winds turn northerly. Key variables include evolving sea-level pressure gradients, 850 hPa temperatures, and boundary-layer moisture, all of which shift rapidly in short-range ensembles and explain the roughly even spread across 11–13°C outcomes. Updated model runs ahead of the 20th will likely tighten these probabilities as the precise steering flow becomes clearer.