Current forecasts from the Met Office and ECMWF models indicate a mild Atlantic airflow over southern England through May 19, with overnight lows expected near 9–11 °C under mostly cloudy skies and light winds that limit radiative cooling. This pattern aligns with typical mid-May climatology for London, where average minima hover around 8–10 °C, yet the absence of a clear anticyclone keeps extreme cooling unlikely. Traders have clustered probability on 10–12 °C outcomes because ensemble runs show only modest day-to-day variability from passing showers, while colder 8 °C or warmer 13 °C scenarios require sharper shifts in cloud cover or wind that models currently rate as lower probability. Updated high-resolution guidance ahead of the date will refine these thresholds.