Forecast models from major centers show a narrow spread in expected overnight minimum temperatures for London on June 27, driven by variable cloud cover and light winds that will modulate radiative cooling under high pressure. Clearer skies in some ensemble members allow greater heat loss, favoring readings near 19–20 °C, while increased humidity and a subtle southerly flow in others limit cooling and support 22–23 °C. The market’s tight clustering around 21–22 °C reflects this model consensus amid typical late-June variability, with resolution hinging on the final 24-hour forecast updates from the Met Office and ECMWF. Urban heat-island effects and precise timing of any frontal passage add further uncertainty to the exact lowest reading.