Recent Met Office guidance points to a minimum of 16°C overnight into June 30 for London, following a period of hot weather and shifting to more moderate conditions with lighter winds. Ensemble forecast spreads from global and regional models introduce uncertainty in overnight radiative cooling rates, influenced by variable cloud cover, humidity levels, and urban heat retention, which can keep readings 1–2°C above rural baselines. This produces tight market-implied odds clustered around 15–19°C, as traders weigh the balance between clearer-sky scenarios favoring lower values and residual warmth or breeze limiting the drop. Updated model runs and any Met Office briefing revisions ahead of the date remain the key near-term catalysts.