Recent Met Office and ECMWF ensemble forecasts for southeast England on May 19 show a lingering cool maritime air mass with variable cloud cover and light southwesterly flow, keeping daytime maxima centered near 16–18 °C. Persistent stratiform cloud has so far suppressed solar heating, while any afternoon breaks could allow brief warming toward 18 °C; conversely, increased drizzle or thicker low cloud would cap readings at 16 °C or below. These narrow thresholds explain why trader-implied probabilities cluster tightly around 16 °C (24.5 %), 17 °C (33.0 %), and 18 °C (32.5 %), with limited conviction on either side until the next high-resolution model runs and official guidance update tomorrow morning.