Recent frontal systems and associated cloud cover over southeastern Brazil have suppressed daytime heating in São Paulo ahead of July 25, keeping maximum temperatures near or below seasonal July averages of 22°C. Official model guidance diverges on the timing of any clearing: persistent low-level moisture and light southerly flow favor highs of 20–21°C if skies remain mostly overcast, while partial breaks in cloudiness could allow greater insolation and push readings to 22°C. Urban heat-island effects at official stations add minor variability, but the narrow spread in market-implied odds (centered on 20–22°C) reflects genuine forecast uncertainty in boundary-layer mixing and precipitation timing rather than any single dominant driver. Updated model runs and INMET observations tomorrow morning will likely resolve the leading outcomes.