Recent ensemble forecasts from the UK Met Office and ECMWF converged on an 18°C daytime maximum for London on May 17 under partly cloudy skies and moderate westerly flow, establishing the market's near-certain 99.7% implied probability for that outcome. These conditions limited solar heating and prevented significant warm-air advection from the Atlantic, aligning with typical mid-May climatology where central London highs average near 17°C. Official temperature readings from stations such as Heathrow or Kew Gardens will confirm the peak, with model agreement reducing the chance of upward revisions. Only unexpected clearer skies or a sudden wind shift could have challenged the consensus and allowed a brief spike to 19°C or above.