Recent ensemble forecasts from the Met Office and ECMWF indicate London’s minimum temperature on June 15 will likely fall between 10–13 °C, with the market’s tight clustering around 12–13 °C reflecting modest model spread in overnight radiative cooling and boundary-layer mixing. Clear or partly cloudy skies under a weakening high-pressure ridge allow greater heat loss after sunset, while light northeasterly winds limit warm-air advection; any increase in low cloud or a subtle frontal passage could raise the minimum by 1–2 °C. Historical June climatology places average overnight lows near 11–12 °C, so current guidance sits close to normal but carries typical short-range uncertainty from small differences in cloud timing and urban heat-island effects. Traders are weighting the latest high-resolution model runs, which converge on 12–13 °C but still permit a slim chance of an 11 °C reading if skies clear fully.