Recent heavy rainfall and persistent cloud cover across Shenzhen have capped daytime heating, anchoring trader consensus around 29–31°C for the August 4 maximum as short-range models show only modest clearing. Subtropical monsoon flow from the South China Sea supplies high humidity and scattered thunderstorms that limit insolation, while urban heat-island effects and weak steering winds keep the diurnal range narrow. Ensemble guidance exhibits small spread in 850-hPa temperatures and boundary-layer moisture, producing the tight clustering between 29°C and 31°C; any shift in convective timing or low-level wind direction could tip the daily peak by 1–2°C. Updated runs from the China Meteorological Administration and global models over the next 24–48 hours will refine these probabilities ahead of market resolution.