**Forecast uncertainty from numerical weather models drives the closely matched market probabilities across 23–28°C for Cape Town’s September 13 maximum.** Cape Town’s spring climate features the cold Benguela Current moderating temperatures, with daytime highs typically ranging 18–22°C under prevailing southeasterly winds. Current short-range guidance shows a mix of partly cloudy to overcast conditions and possible light showers or thunderstorms, which would suppress heating through reduced insolation and evaporative cooling. Model differences arise mainly from the exact timing and strength of any Atlantic trough or cold front, variable low-level moisture, and wind shifts that could either enhance or limit afternoon warming. Historical September variability and the proximity of resolution amplify this spread, producing the observed trader consensus around the middle of the likely range. Updated model runs and official South African Weather Service guidance over the next 48 hours will be key catalysts.