Recent Met Office guidance and European ensemble model runs have converged on a daytime maximum of 21–22 °C across London under partly cloudy skies and light south-southeasterly flow, anchoring trader consensus at exactly 21 °C. Official temperature observations, recorded at standard Met Office sites using calibrated instruments, currently align with this narrow range, leaving little room for deviation once the daily highest is confirmed. Historical June averages near 19–20 °C provide climatological context, but the current stable synoptic pattern and absence of strong insolation or advection limit upside potential. The only realistic challenges would involve unexpected convective bursts or slight shifts in cloud cover timing that alter the precise peak recorded at the official stations before resolution.