Recent model consensus from the Met Office and European ensembles points to overnight lows of 9–11 °C in central London on May 17, driven by an approaching Atlantic front that will increase cloud cover and limit radiational cooling after sunset. Light south-westerly winds of 5–10 mph should further moderate temperatures by mixing boundary-layer air, while scattered showers add slight uncertainty to the precise minimum. Mid-May climatology at Heathrow places the average low near 8 °C, so current guidance sits slightly above normal yet remains sensitive to the exact timing of frontal passage and any brief clear spells that could allow deeper cooling toward 8 °C. Traders are weighting these factors against ensemble spread, with the tight clustering between 10 °C and 11 °C reflecting the narrow range of plausible outcomes under the latest runs.