The arrival of a polar air mass advected northward by strong southerly winds is the dominant factor shaping trader sentiment for Buenos Aires minimum temperatures on September 6. Official Servicio Meteorológico Nacional guidance and multiple model runs center on a low near 2°C under clear to partly cloudy skies, well below the September climatological average of about 9°C, with radiative cooling overnight amplifying the drop after a brisk daytime high around 10-12°C. Ensemble spreads and slight differences in cold-front timing introduce uncertainty around whether readings settle near 0-1°C or hold a degree or two higher, explaining the tight clustering of implied probabilities across single-digit outcomes and the modest tail risk priced for sub-zero values. Fresh model guidance overnight will likely tighten the range before resolution.