Latest National Weather Service guidance and ensemble model runs for Seattle place the May 17 high squarely in the low-to-mid 60s, driven by persistent onshore marine flow off the Pacific that caps afternoon warming. This pattern aligns with mid-May climatology, where average highs at Sea-Tac International Airport hover near 63–66 °F amid moderate sea-surface temperatures and limited solar heating under variable cloud cover. Traders have priced the 62–63 °F bin highest at 39 % because recent model updates show minimal spread around that narrow range, while the 64 °F-or-higher bucket at 29 % reflects residual uncertainty over any late-day clearing. Lower outcomes remain discounted given the absence of strong cold-air advection or widespread stratus that would suppress readings below 60 °F.