**Strong northwesterly flow and the timing of rain clearance on September 4 are the dominant drivers of trader positioning around a 9–12 °C overnight minimum in Wellington.** Current MetService and ensemble guidance show persistent strong northwesterlies (15–25 m/s) through the day, moderating temperatures while a front clears from the southwest, leaving clearer skies by evening. This setup favors radiational cooling under reduced cloud cover, but the strength and persistence of the gradient wind will limit how far the mercury can fall. Historical climatology places the typical September 4 minimum near 9 °C (48 °F), with a narrow interquartile range of roughly 8–11 °C. Model spreads arise mainly from differences in forecast wind deceleration after frontal passage and residual moisture affecting dew-point depression. Stronger, sustained northwest winds keep the boundary layer well-mixed and push the lowest temperature toward 11–12 °C; lighter winds and clearer skies allow greater surface cooling, supporting 9 °C or slightly below. Dew-point forecasts clustered around 5–8 °C further cap how low readings can go without additional advection of colder air. The closely bunched market-implied probabilities around 9–14 °C therefore reflect genuine short-range forecast uncertainty rather than disagreement over the broader synoptic pattern. Updated model runs and MetService guidance issued in the next 24–36 hours—particularly refinements to wind and cloud fields after 18 UTC on the 3rd—will be the key catalysts that shift odds among these adjacent outcomes.