Recent Met Office forecasts indicate mild conditions over London through May 21, with a mix of sunny intervals and light showers supporting overnight lows primarily in the 11–13 °C range under southwesterly flow. This positioning explains the market’s emphasis on 12 °C and 13 °C outcomes, as cloud cover and warmer air advection limit radiative cooling compared with typical mid-May climatology of 7–9 °C. Model consensus shows limited intensification of any northerly chill, keeping the probability of sub-10 °C readings low while still allowing for modest day-to-day variability from frontal passages. Traders are therefore assigning the highest implied odds to the 17 °C-or-higher bin, reflecting the current warm spring pattern across northwest Europe and the absence of strong high-pressure setups that would otherwise drive sharper nocturnal drops.