Persistent high pressure across southern England, combined with an ongoing heatwave featuring daytime maxima near 33°C, is suppressing radiative cooling and elevating overnight minimums in London. Met Office guidance currently projects a 21°C low for July 8 under light winds and mainly clear skies, with the urban heat island effect adding 2–4°C retention relative to rural baselines. Model consensus shows limited variability in steering patterns or cloud cover through the period, though small shifts in wind speed or timing of any Atlantic moisture could allow greater cooling toward 18–19°C. Traders appear to balance this forecast against historical July climatology (typical lows 13–15°C) and residual uncertainty in precise station readings, keeping 17°C-or-below and 20°C outcomes nearly tied near 45–47% implied probability.