Recent Met Office guidance points to a maximum of 17 °C in London today under a mild south-westerly flow, with traders assigning nearly equal weight to 16 °C and 17 °C because model runs differ on the timing and extent of cloud breaks. Persistent Atlantic low pressure maintains a cool maritime air mass, limiting insolation while scattered showers and variable stratiform cloud reduce peak surface heating by several degrees. Urban heat-island effects at central stations versus official sites such as Heathrow can add 1 °C locally, yet stronger winds enhance mixing and suppress that increment. Ensemble spread in short-range guidance therefore centers probabilities tightly around the 16–17 °C threshold, with any late-day clearance or heavier rain the key variable that would shift the recorded high.