Latest Met Office and multi-model guidance, including ECMWF ensembles, point to a maximum of 22°C in London on October 5 under stable high pressure, light westerly flow, and limited cloud cover that allows modest daytime warming without strong advection of warmer air. This mild early-autumn pattern, several degrees above the long-term October average, underpins the market’s leading 47% implied probability for 22°C, with 21°C and 23°C shares reflecting minor spread in peak timing and boundary-layer mixing across runs. Forecasters note high ensemble agreement for this range, though final observed values depend on precise insolation and urban heat effects at the recording station.