A strong high-pressure system and southerly airflow have driven an exceptional heatwave across southern England, producing warm, humid nights that limit radiative cooling and keep minimum temperatures elevated. Official Met Office guidance for 26 June projects a nighttime low near 21°C in London, consistent with the market’s leading 19°C outcome at 34.5% and clustered probabilities around 20–23°C. Key variables include the exact timing of any weakening in the ridge, cloud-cover evolution that could enhance or suppress overnight cooling, and minor model spread in boundary-layer moisture. With resolution only 48 hours away and ensemble guidance still showing modest variability, traders are pricing in a narrow but uncertain range centered on these unusually high June minima rather than typical climatological values near 12–14°C.