**Northwesterly winds and a forecast clearing trend after morning showers are the main drivers positioning 17–18°C as the leading outcomes for Wellington’s daily maximum on September 4.** Local forecasts, including from NZ sources, indicate a high near 17°C with showers easing to fine conditions in the afternoon under strengthening northwesterlies. These conditions favor modest warming despite cloud and precipitation, as the flow draws milder air and allows some solar heating once skies clear. Official and model guidance clusters around 15–17°C, with a few runs reaching 18°C if clearing occurs earlier or winds enhance downslope warming. The market’s heavy weighting toward 18°C (56%) and 17°C (34.5%) reflects trader consensus on this range, incorporating recent forecast updates that emphasize the northwest regime and afternoon improvement. Lower probabilities for 16°C or below align with limited downside risk from persistent rain or stronger onshore flow, while outcomes above 19°C remain marginal given seasonal norms and model spread. Updated model runs and any MetService briefing on wind strength or timing of clearance represent the key near-term catalysts that could shift these implied probabilities.