Trader consensus on Polymarket has locked in a 100% implied probability for Beijing's highest temperature reaching exactly 21°C on April 28, driven by the China Meteorological Administration's (CMA) latest forecast projecting this maximum under persistent cloudy skies and northerly winds, which limit solar heating and convective warming. Current observations from Beijing's meteorological stations align closely, with daytime readings peaking near this threshold amid overcast conditions that have characterized the past week, cooler than the late-April climatological average of around 22°C. Model consensus from regional forecasts reinforces stability, though a realistic challenge could arise from unexpected prolonged clearing in the afternoon, potentially enabling brief spikes to 22°C via enhanced insolation; official end-of-day data from CMA will resolve the market.