A persistent cold front and influx of polar air that arrived around September 12 have kept São Paulo under dense cloud cover and steady rain, suppressing overnight lows on the 14th near the seasonal average while making this September the wettest on record since 1943. Official measurements from stations such as Mirante de Santana reflect this compressed diurnal range, with trader consensus split almost evenly between 13 °C and 14 °C as the precise minimum because minor differences in model timing, station siting, and radiational cooling under overcast skies can shift the recorded low by a degree. Upcoming Inmet verification and any revised hourly data releases remain the key catalysts that could tip the narrow margin between these two leading outcomes.