Official National Weather Service observations from the automated sensors at San Francisco International Airport (KSFO)—the market's resolution source—confirm the highest temperature on May 13, 2026, reached 64-65°F based on verified hourly data finalized via Wunderground summaries. This reflects typical May marine layer persistence, with cool onshore winds and stratus clouds capping daytime heating below the climatological average high of 65°F, as persistent Pacific inflow limited solar insolation and mixing. Trader consensus at 99.9% implied probability underscores this strong evidentiary alignment, with skin-in-the-game bets aggregating real-time ASOS measurements. Realistic challenges are negligible post-finalization, barring rare NWS data revisions from quality control audits expected within 24-48 hours, which historically affect less than 0.1% of routine observations.