Trader consensus on Polymarket tilts slightly toward 68°F or higher at 50.5% implied probability for San Francisco's highest temperature on May 16, driven by National Weather Service forecasts and ensemble models projecting highs of 64-71°F amid a developing upper-level ridge promoting inland warming and partial marine stratus burn-off. Recent KSFO observations reflect this variability—71°F on May 11 followed by mid-60s mid-week—highlighting coastal cooling from persistent Pacific onshore flow, which tempers diurnal heating despite May averages near 67°F. The clustered 36% odds for 62-67°F bins underscore model spread on boundary layer depth and stratus persistence; lower outcomes trail due to climatological rarity below 60°F this late in spring. New 12z GFS/ECMWF runs expected May 15 could sharpen resolution criteria tied to official SFO measurements.