Latest numerical weather prediction ensembles from global models indicate Shanghai’s May 18 maximum temperature will most likely peak between 26–28 °C, consistent with the market’s tight clustering around those outcomes. Mid-May climatology in the Yangtze River Delta features strengthening subtropical high pressure that favors clear to partly cloudy skies and moderate southerly flow, promoting daytime radiative heating while limiting extreme warming. Minor differences among 26 °C, 27 °C, and 28 °C hinge on afternoon cloud timing and boundary-layer mixing; current guidance shows stable conditions with limited moisture advection, keeping the probability of exceeding 29 °C low. Official resolution will rely on the China Meteorological Administration’s highest reading at the Shanghai Pudong International Airport station.