The market's overwhelming consensus on 12°C as London's lowest temperature for September 9 stems from official Met Office observations across multiple London stations confirming this minimum overnight reading. A stable high-pressure system has suppressed further cooling, keeping temperatures consistent with late-summer climatology where September minima typically range 10-13°C. Real-time data from ground stations show no dips below this threshold, with model runs aligning closely on the outcome. Final daily verification reports expected shortly could refine details, though revisions appear unlikely given station agreement. Only an unforeseen data anomaly or boundary adjustment would realistically alter the current positioning.