Recent Met Office and ECMWF ensemble forecasts point to a London maximum of 15–16 °C on May 17, driven by moderate westerly flow advecting cooler Atlantic air across southern England under mostly cloudy skies with possible light showers. This setup keeps daytime heating near the mid-May climatological average while limiting the potential for stronger solar insolation that could push readings to 17 °C or higher. Traders have clustered probability tightly around the 15 °C and 16 °C outcomes because afternoon cloud cover and the precise timing of any Atlantic frontal passage remain the dominant sources of forecast spread; clearer breaks would favor the upper end of the range, whereas persistent overcast or earlier rain would favor the lower. New model runs overnight will likely refine these variables ahead of resolution.