Recent Met Office observations and forecast models have driven near-certain trader consensus on a 20°C daily maximum for London on September 16, aligning closely with the 1991–2020 climatological average high of 20.1°C at Heathrow. Stable high pressure, light southwesterly winds, and minimal cloud cover supported gradual daytime warming to this level without exceeding typical late-summer variability. Official station data, including Heathrow’s recorded peak near this threshold, reinforced the outcome ahead of final verification. A modest revision in post-processed readings or station-specific criteria could theoretically shift resolution, though current evidence from NOAA and Met Office sources shows little room for deviation outside the narrow 19–21°C band.