The Hong Kong Observatory's official daily maximum of exactly 25°C on May 16, recorded at its principal urban stations under standardized Stevenson screen conditions, has driven near-certain trader consensus on that outcome. This reading aligns with a stable subtropical high-pressure system that promoted subsidence, widespread cloud cover from a moist easterly flow, and limited daytime solar heating during the pre-monsoon transition period. Climatological baselines for mid-May show typical highs of 28–29°C, so the cooler anomaly reflects measurable synoptic suppression rather than model uncertainty. While official data leave little room for revision, an undetected instrumentation anomaly or post-hoc quality-control adjustment at the Observatory could theoretically reopen the market, though historical precedent for such changes on daily maxima remains exceedingly rare.