**Forecast models indicate the lowest temperature in São Paulo on September 5 will likely fall in the 13–17°C range, with market-implied probabilities clustering tightly around 14–17°C.** This reflects consensus from short-range numerical weather prediction outputs showing a shift from recent warm, dry conditions (highs near 26–28°C) to a cooler, moister air mass associated with an approaching frontal system. Key drivers include increased cloud cover and precipitation chances (patchy rain or showers noted in multiple runs), which limit nighttime radiative cooling compared to clear-sky scenarios. Dew points near 14–15°C and light winds further constrain how low surface temperatures can drop overnight. Model guidance shows minor spread in the exact minimum, driven by differences in timing and intensity of rain, boundary-layer moisture, and urban heat retention in the São Paulo metro area. Historical early-September climatology places typical overnight lows near 12–14°C, so the current setup sits slightly above average but aligns with the incoming disturbance. Updated model runs and official monitoring agency briefings over the next 24–48 hours will likely tighten the distribution as the event nears resolution.