**Recent model consensus and an incoming southerly change are the main drivers keeping 14–15 °C as the market leaders for Wellington’s highest temperature on 22 September 2026, even as fresh forecasts trend cooler.** Wellington’s September climatology shows average daily maxima near 13–14 °C, with highs rarely exceeding 16 °C or falling below 11 °C. Current observations place the region in a mild northerly flow that produced 13–15 °C readings on 19–20 September. However, guidance from multiple sources (including WeatherBug, PredictWind, and Met Office runs) now indicates a strengthening southerly flow and associated cold front arriving overnight 21–22 September. This setup favors widespread cloud, 70–90 % rain probability, and daytime maxima of 12–14 °C, with the highest readings most likely in the early afternoon before the change fully establishes. The elevated 62.5 % implied probability on 15 °C and 25 % on 14 °C therefore reflects residual uncertainty in the exact timing and intensity of the front, plus the possibility that sheltered or airport stations could still record a brief 14–15 °C peak if the cooler air arrives later than modeled. Lower outcomes (13 °C and below) carry smaller probabilities because they would require either an earlier or stronger southerly surge than currently indicated. Updated model runs and official MetService or NIWA guidance over the next 24–48 hours will be the key catalysts likely to shift these market-implied odds.