Recent Met Office and ECMWF ensemble forecasts indicate a mild southwesterly flow over southern England on May 19, supporting daily highs clustering between 17°C and 18°C amid partly cloudy skies and light winds. Model consensus remains tight, with only minor spreads arising from the exact timing of any passing showers or breaks in cloud cover that could nudge the peak by 1°C. This positions the two leading outcomes nearly even, reflecting traders’ assessment of genuine forecast uncertainty rather than a single dominant scenario. Historical mid-May climatology for London shows average highs near 16–18°C, providing context that current guidance aligns closely with seasonal norms without strong signals for unusual warmth or cooling. Updated model runs expected later today will likely refine these probabilities ahead of market resolution.