Official forecasts from MetService New Zealand and supporting ensemble model runs establish a daytime maximum of 14°C for Wellington on May 17, driving the market's near-certain 99.7% implied probability on that outcome. This aligns with mid-autumn climatology in the Southern Hemisphere, where moderate southerly winds, persistent high cloud cover, and reduced solar insolation typically limit warming to near the long-term May average high. Resolution depends on the highest official reading at primary stations, with current model consensus showing minimal divergence. A late-day shift to clearer skies or enhanced northerly flow could briefly elevate readings, though such changes remain unlikely given stable synoptic patterns and the tight forecast window.