Trader consensus on Polymarket splits evenly at 50% implied probability between a cool high of 21°C or below and a hot 31°C or higher in São Paulo on April 14, reflecting sharp divergence in forecast models amid autumnal weather volatility. Recent cold fronts sweeping Southeast Brazil—most notably impacting the region around April 8-9 with rain, gusts up to 80 km/h, and temporary temperature drops—have heightened uncertainty about whether southerly winds and cloud cover from lingering instability will suppress daytime highs below 22°C, or if subtropical high pressure regains dominance for clear skies and radiative heating pushing above 30°C. INMET and CPTEC guidance shows model ensembles clustering near climatological norms of 24-27°C but with wide spreads; key differentiators include frontal timing, low-level moisture advection, and urban heat effects at official measurement sites. Watch for updated GFS/ECMWF runs and INMET bulletins by April 13 evening.