Recent southerly winds and a pulse of cooler polar air have positioned Wellington for a below-average maximum on August 16, with official guidance from MetService and NIWA pointing to a high near or slightly above 10 °C under cloudy, showery conditions. August climatology places the typical daily maximum at 12 °C, yet strong southerlies suppress daytime warming by advecting maritime air and limiting solar heating. Ensemble forecasts show limited spread around the 9–11 °C range, with 10 °C emerging as the mode because model consensus favors persistent cloud cover and light showers that cap afternoon temperatures. Traders assign the bulk of probability to this narrow band because resolution depends on the official MetService observation at Kelburn, which is sensitive to small shifts in wind strength or timing of any clearing. Updated model runs overnight will determine whether probabilities migrate toward 11 °C if southerlies weaken earlier than expected.