Latest MetService guidance projects an 18°C daily maximum for Wellington on May 31 under a stable northerly flow and partly cloudy regime typical of late autumn. This aligns with regional climatology, where cool maritime air from Cook Strait caps diurnal warming and produces low day-to-day variance. Numerical weather prediction runs show tight clustering around this value, with minimal model spread supporting the market’s near-certain pricing. A prolonged clear spell or abrupt wind shift could allow brief solar heating toward 19°C, while increased cloud or a frontal passage might hold the high at 17°C or below, though current observations and guidance indicate limited likelihood of such deviations before resolution.