**Persistent southwest monsoon (habagat) activity and associated heavy rainfall are the dominant drivers keeping Manila's minimum temperature on August 29 clustered tightly around 25–26°C in forecasts.** Official PAGASA guidance and multiple model runs show cloudy skies with scattered to heavy thunderstorms, moderate-to-strong southwest winds, and high humidity (often 85–95%), which limits nocturnal radiative cooling and holds overnight lows near the seasonal average of 25–26°C. An LPA east of northern Luzon adds uncertainty but is not yet steering the monsoon strongly, so its influence on exact minimums remains limited. This produces the narrow distribution reflected in market odds, with 24–26°C outcomes trading near parity because small differences in cloud cover, rainfall timing, or wind gusts can shift the recorded low by 1–2°C. Historical analogs for late-August Manila under similar monsoon regimes rarely deviate far from this band, reinforcing the tight clustering while leaving room for model divergence on the precise hourly minimum.