Recent forecast models from the China Meteorological Administration indicate increased cloud cover and light rain potential over Shanghai around May 21, favoring overnight lows near or below the seasonal mean and elevating the 15°C-or-below outcome to a 40.5% market-implied probability. Shanghai’s mid-May climatology typically features nighttime minima of 16–18°C under clear subtropical high pressure, yet current steering patterns and moisture advection from the East China Sea introduce downward variability. Traders assign secondary weight to 18°C and 19°C bins at 20–22% each, reflecting the tight distribution of historical station data and model spread. Official guidance updates expected in the next 48 hours will refine landfall timing for any frontal boundary and further shape resolution odds.