Official observations from the Hong Kong Observatory established a daily maximum temperature of 27°C on May 15, 2026, under persistent overcast skies, 83–89% relative humidity, and widespread thundery showers tied to a low-pressure trough over the South China Sea. This verified station reading, consistent with mid-May subtropical climatology where daytime highs typically range 26–29°C, anchors the market’s near-certain 27°C outcome as traders incorporate the precise resolution data rather than forecasts. Realistic challenges to this result would require abrupt sky clearance, sharply reduced humidity, and stronger solar insolation allowing prolonged radiative warming, though such conditions were absent amid the active trough and elevated moisture.