The close split between 16°C (43%) and 15°C (41%) market-implied odds for Wellington's September 27 high stems from forecast uncertainty around an approaching cold front and associated wind shift. Official MetService guidance and ECMWF runs point to a rainy, windy day with strong west-southwesterlies developing, limiting daytime heating and capping the maximum near 14°C after early northerlies. Brief clearing or timing variations in the frontal passage could allow a brief spike toward 15–16°C, while historical September climatology averages around 13°C. Strong winds and precipitation reduce diurnal temperature range, keeping the tight trader consensus focused on these two outcomes ahead of updated model runs.