Short-range ensemble forecasts from the Met Office and ECMWF currently anchor trader sentiment on 17–18°C as the most probable minimum temperature in London on June 20, with those outcomes holding near-even implied probabilities. Building high pressure is drawing warmer air northward, raising overnight lows above recent cooler baselines while limiting radiative cooling under partly cloudy skies. Key differentiating variables include precise cloud-cover timing, boundary-layer wind speeds, and London’s urban heat-island effect, all of which can shift the recorded minimum by 1°C between adjacent model runs. Updated guidance expected within 24–48 hours will narrow uncertainty ahead of market resolution.