**Trader sentiment for London's lowest temperature on August 4 centers on the closely matched 20°C (40%) and 21°C (41%) outcomes, reflecting short-range model consensus around 19–21°C minima amid a warm, settled pattern.** Current Met Office guidance indicates a daytime high near 28°C and overnight low around 19°C, consistent with light winds and residual warmth from an above-average summer featuring record-high nighttime temperatures. High pressure has promoted clear or partly cloudy skies, limiting radiative cooling and supporting elevated minima, while the broader seasonal signal of 1–2°C above the 1991–2020 average reinforces trader expectations for values near or slightly above the climatological norm of roughly 14–17°C. Differentiating the leading bins hinges on subtle forecast uncertainties: minor model disagreements on cloud cover (which traps heat) versus clearer skies (enhancing cooling), plus small variations in wind speed and the precise timing of any weak frontal influence that could briefly lower temperatures. With resolution based on official Met Office observations, traders weigh these factors against the low probability (<2% combined) of cooler outcomes below 18°C given the prevailing synoptic setup.