Current forecast models from sources including GFS data and the Met Office indicate overnight lows in London on September 27 near 12–14 °C, driven by a mild southerly airflow and increasing cloud cover with scattered showers that limit radiative cooling. Historical September minima average around 9–10 °C, but recent model runs show warmer conditions persisting due to the absence of clear anticyclonic setups. This uncertainty in exact minimum temperature—particularly whether cloud and precipitation effects push the low to 12 °C versus 13 °C—explains the closely matched market-implied odds, with lower probabilities assigned to cooler outcomes requiring stronger northerly advection or clearer skies not currently favored. Updated model guidance ahead of the date will likely refine these ranges.