Recent National Weather Service model runs and supporting numerical guidance have converged on a daily high near 58–59 °F at Seattle-Tacoma International Airport, driving the market’s near-certain pricing for that bin. Persistent onshore flow from the cool Pacific marine layer, combined with limited diurnal heating under a stable May pressure pattern, has kept temperatures close to seasonal normals rather than allowing typical late-spring warming. Historical climatology for mid-May shows average highs around 65 °F, but current conditions reflect stronger-than-normal coastal influence that suppresses afternoon peaks. Minor forecast adjustments in the final 12–24 hours remain the only realistic path to a different outcome, as any unexpected clearing or reduced marine stratus could add a degree or two before official verification.