**Recent passage of a cold front into São Paulo around June 23 is the dominant driver of trader positioning.** The front has advected cooler polar air into the region, with models indicating suppressed daytime highs for June 25 amid increased cloud cover, light rain or drizzle, and limited solar heating—conditions typical after winter’s official start on June 21. Official guidance points to minimums near or below 10–13 °C overnight into the 25th, with maximum temperatures likely constrained to the 14–17 °C range rather than the seasonal average near 21–22 °C. **Model consensus and timing uncertainties explain the tight clustering around 14–15 °C (over 60 % combined implied probability).** Differences in the speed of cold-air advection, residual moisture, and any late-day clearing produce small but market-relevant variations in peak readings. Traders are weighting the most recent runs showing a modest rebound from the immediate post-frontal chill while still reflecting the overall cooler regime. No major warm-air return or strong subsidence is expected before the 25th, keeping probabilities for 18 °C+ or sub-13 °C outcomes very low. Updated INMET and regional model guidance on the 24th–25th will be the next key inputs for positions.