Recent Met Office forecasts for London indicate a daytime high of 15°C under mostly sunny intervals with light winds and stable high pressure, aligning closely with seasonal averages for mid-May. Ensemble model runs show minimal spread around this value, reflecting typical springtime conditions without significant warm advection from the south or Atlantic influences that could drive higher readings. This strong scientific consensus underpins the near-certain market positioning at 15°C. A realistic shift to 16°C or above would require unforecasted increases in insolation, a sudden change in air mass, or localized urban heat effects exceeding official station measurements, none of which current guidance supports as likely before the day ends.