Persistent cloud cover, widespread rain, and high humidity from an active frontal system are capping solar insolation and limiting daytime heating in São Paulo on September 10, keeping the maximum temperature tightly clustered near 22–24 °C. Official guidance from the CGE and Met Office indicates morning temperatures around 17–19 °C rising only modestly under overcast skies, with afternoon showers and gusty winds further suppressing peaks. This aligns with trader emphasis on the 22 °C outcome (28 % implied probability), while the spread across 21–24 °C reflects model uncertainty in exact rainfall timing and intensity. Historical September averages near 23 °C provide context, yet the current unstable pattern favors values at or below that baseline. Updated radar and model runs through the afternoon will clarify whether any brief clearing allows a brief spike toward 25 °C.