Recent Met Office and ensemble model guidance point to a moderating airmass over southern England after the mid-August heatwave peak, with maximum temperatures in London on the 15th most likely reaching 26–27 °C under a mix of sunny intervals and increasing cloud. Subtle differences in the timing of Atlantic frontal progression and residual high pressure determine whether daytime highs settle at 26 °C or edge to 27 °C, producing the tight market spread between these two outcomes. Ensemble members show limited spread beyond that range, consistent with the lower probabilities assigned to 25 °C or 28 °C and above. Updated short-range runs tomorrow morning will refine boundary-layer mixing and any localized sea-breeze effects that could nudge the official reading at the verification station.