Current numerical weather prediction models, including ECMWF and GFS ensembles, indicate Shanghai’s overnight low on May 19 will likely settle near 20–21 °C under light southerly flow and partial cloud cover that moderates nocturnal radiative cooling. Mid-May climatology shows typical minimums of 17–22 °C at Shanghai Pudong station, with the narrow spread among 19–21 °C outcomes reflecting small forecast differences in wind speed and cloud thickness that can shift the low by 1–2 °C. Recent days have seen similar conditions after a continental air mass departed, allowing seasonal warming while the urban heat island effect adds roughly 1 °C to minima. Final model runs and official China Meteorological Administration guidance over the next 48 hours will clarify whether any clearing or subtle wind shift pushes the reading lower or higher.