Recent forecast model consensus for São Paulo points to a daytime high on October 4 in the mid-to-upper 20s Celsius, with Met Office guidance at 28°C and several regional runs clustering near 26–27°C amid variable cloud cover and light rain potential. Northwest wind advection and a passing frontal boundary introduce the key uncertainty: stronger insolation during breaks could push readings toward 28–29°C, while persistent overcast or precipitation suppresses the maximum closer to 24–25°C. These short-range differences explain the tight market clustering between 24°C and 28°C outcomes, as traders weigh the latest ensemble spreads and observed cooling trends from the prior two days against climatological October averages near 25°C. Updated model runs and morning observations will refine resolution criteria ahead of the daily peak.