**Trader sentiment for Shanghai’s lowest temperature on June 15 centers on 20–22 °C outcomes because short-term forecasts and climatological norms converge there.** Mid-June in the Yangtze River Delta features subtropical monsoon conditions with average overnight lows of 21–22 °C, rising seasonal humidity, and the onset of the plum-rain (Meiyu) period that brings frequent cloud cover and light showers. These factors limit nocturnal radiative cooling, keeping minima from dropping much below 20 °C or rising above 23 °C. Recent model guidance shows daytime highs near 25–27 °C under variable easterly flow, producing modest diurnal ranges consistent with early-summer patterns. Overcast skies and elevated moisture further compress the temperature spread, supporting the market’s heavy weighting toward 22 °C (38.5 %) followed by 21 °C and 20 °C. No major synoptic anomalies—such as strong cold advection or clear, dry nights—are indicated in current outlooks, so probabilities remain anchored to historical baselines rather than outlier scenarios. Updated NWP runs and official agency briefings over the next 24 hours will refine these implied probabilities as the overnight period approaches.