Trader sentiment for Guangzhou’s peak temperature on May 19 clusters tightly around 28–29 °C because ensemble forecasts show a classic late-spring subtropical setup with warm, moist southerly flow from the South China Sea under the western ridge of the subtropical high. Minor differences in predicted cloud cover, boundary-layer mixing, and afternoon convection account for the narrow spread between 28 °C and 30 °C outcomes; stronger onshore winds or reduced cloudiness could nudge readings upward, while increased thunderstorm activity would cap them. Global models such as ECMWF and GFS continue to converge on this range, with the next high-resolution updates expected to tighten probabilities as the date approaches.