**Forecast uncertainty in cloud cover, rainfall timing, and humidity is driving the near-even split between the 20°C-or-below and 30°C-or-higher minimum outcomes.** Kuala Lumpur’s equatorial climate normally produces September overnight lows near 24°C amid high humidity and frequent convection. Current model runs show disagreement on whether persistent cloud and heavy showers—common during the inter-monsoon period—will suppress daytime heating while trapping heat overnight, or allow clearer intervals that permit greater nocturnal cooling. Official guidance from regional meteorological centers places the expected minimum in the mid-20s°C range, but small shifts in storm timing or moisture advection can swing the actual low by several degrees, explaining why traders assign roughly equal weight to the two extreme brackets while spreading the remainder across the 21–29°C band. Updated model consensus and satellite observations over the next 48 hours will likely narrow this range.