Recent Met Office guidance and ensemble model runs indicate a warm southerly airflow dominating southern England through mid-June, supporting overnight minima near 17–18°C for London on June 19. Limited nocturnal radiative cooling under partly cloudy skies and modest wind speeds reduces the potential for sharper drops, while urban heat-island effects in central areas further anchor temperatures above seasonal climatological averages of 12–13°C. Ensemble spread remains modest but centers on this range, with small probabilities for 16°C or lower tied to any unexpected clearer interludes or northerly perturbations. Updated high-resolution forecasts and observational data from Heathrow and other London stations over the next 48 hours will refine these thresholds ahead of market resolution.