Official forecasts from the Met Office and supporting models show a maximum of 21°C for London on October 15, with mostly cloudy skies, sunny intervals, and only a low 18–30% chance of rain under southwesterly flow. This above-average reading—versus the 1991–2020 October 15 mean high of 15.8°C—reflects a mild Atlantic air mass that has kept recent days warmer than typical. Ensemble guidance shows limited spread around the 20–22°C range, with minimal upside risk from further warming or downside from earlier cooling. The market’s concentration on 21°C and 22°C therefore aligns with the latest model consensus and the narrow uncertainty band ahead of overnight resolution.