Trader sentiment centers on ensemble forecasts from the Hong Kong Observatory and global models projecting a daily maximum of 27–28°C on May 18, consistent with mid-May subtropical climatology where average highs reach 28°C amid rising humidity. Persistent southwest monsoon flow delivers moist air masses and variable cloud cover that limit solar heating and keep boundary-layer mixing modest, narrowing the likely range. Small differences in forecast dew-point depression or low-level wind shear could determine whether the official station reading hits 28°C or stays at 27°C, with traders weighting recent model runs showing minimal spread. Resolution will hinge on the Observatory’s verified maximum, recorded under standard Stevenson screen conditions.