Official meteorological observations from Argentina's National Meteorological Service confirmed a daily maximum of 18°C in Buenos Aires on September 4, 2026, under clear to partly cloudy skies following a cold front passage. Stable high pressure, light southwest winds, and low humidity supported gradual daytime warming from morning lows near 8–9°C to the afternoon peak, aligning with seasonal September averages around 19°C. Multiple forecast models converged on this range with minimal spread, producing the market's near-certain 18°C outcome. Only revised station data or localized microclimate differences at official recording sites could realistically alter the result, though such adjustments remain rare after initial verification.