Recent National Weather Service guidance and ensemble model runs point to a daytime high in the low-to-mid 70s for San Francisco on May 17 as a weakening marine layer allows greater solar heating under building high pressure. This pattern deviates from the city’s typical May climatology, where persistent onshore flow and coastal stratus often cap highs near 67 °F at the airport station. Current forecasts show afternoon temperatures climbing quickly once low clouds erode, with light northwest winds supporting modest mixing rather than strong cooling. The market’s 61.5 % implied probability on 68 °F or higher reflects trader assessment of this warming potential, while the 28 % on 66–67 °F accounts for residual uncertainty if stratus lingers longer than projected. Final resolution hinges on the official peak reading at San Francisco International Airport tomorrow evening.