Hong Kong Observatory observations and forecast models drove the overwhelming trader consensus toward a 27°C maximum on May 15, as a trough of low pressure triggered persistent cloud cover, high relative humidity of 83–89 percent, and frequent thundery showers that suppressed daytime heating. These conditions aligned with mid-May climatology, where typical maxima hover near 28°C but moist, overcast setups often limit peaks to the mid-20s. Official hourly readings at the primary station repeatedly reached but did not exceed 27°C, confirming the market-implied probability above 99 percent. A realistic challenge would require rapid sky clearing and prolonged solar insolation to push temperatures to 28°C or higher, though ongoing showers and the stable steering pattern made such shifts improbable before final daily maximum confirmation.