Recent ensemble forecasts from the Global Forecast System and European Centre for Medium-Range Weather Forecasts models indicate a daytime high near 27–28°C for Shenzhen on May 17, reflecting modest cloud cover and humidity typical of the Pearl River Delta’s early monsoon transition. Mid-May climatology shows average highs of 29–30°C, but a developing low-pressure system is expected to limit solar heating and produce scattered showers, capping peaks below historical norms. This setup creates tight differentiation between 27°C and 28°C outcomes, with small shifts in rainfall timing or wind patterns able to tip the balance. Traders assign the highest implied probability to 28°C at 33.5 percent, followed closely by 27°C at 27 percent, underscoring the narrow scientific margin ahead of tomorrow’s official observations.