Official Met Office observations and Heathrow station data established a daily maximum of 18°C on October 12 under overcast skies with light southwesterly winds and high humidity, aligning precisely with the market's near-certain 18°C outcome. This exceeded the 1991–2020 average high of 16.3°C for the date amid a mild autumn pattern, while model consensus and real-time reports ruled out cooler readings. The strong scientific consensus from verified station measurements underpins trader positioning, though minor resolution risks remain from potential station-specific discrepancies or final quality-controlled revisions.