Latest ensemble forecasts from the Met Office and European models indicate overnight minimums in London on June 18 centering near 16–17°C, driven by a mild Atlantic airmass, moderate cloud cover limiting radiative cooling, and light winds that reduce boundary-layer mixing. These conditions have nudged market-implied odds toward 17°C (45%) and 16°C (39%), reflecting tight uncertainty around the exact low at the London City Airport station. Historical mid-June climatology at Heathrow averages closer to 12–13°C, so current guidance points to above-normal values; any last-minute increase in clear skies or northerly flow could drop readings toward 15°C, while persistent stratus would favor the higher end of the range. Updated model runs and official guidance issued within 24 hours of the observation window will likely resolve the narrow spread between the two leading outcomes.