**Trader sentiment for the lowest temperature in Wellington on September 21 reflects genuine forecast uncertainty in a highly variable springtime setting.** Current model runs show a range of possible overnight minima, with some ensembles favoring radiative cooling under clearer skies or lighter winds that could push readings to 3°C or below, while others indicate persistent northerly flow or cloud cover holding lows near or above 13°C. Wellington’s exposed coastal position amplifies sensitivity to wind direction shifts and pressure gradients, which can swing temperatures several degrees within hours. Recent spring patterns have featured sharp day-to-day contrasts, including cold fronts and frost risks, adding to the spread. Official guidance from MetService and international models diverges on the exact timing and strength of any clearing or frontal passage over the next 48 hours, keeping the market-implied odds nearly even between the extreme bins. Updated runs from agencies such as the Met Office and ECMWF ensembles will likely narrow the range before resolution.