**Ongoing southwest monsoon activity, including scattered rains and thunderstorms across Luzon, is the main driver keeping Manila’s expected minimum temperature near 27°C on September 2.** Persistent cloud cover and high humidity (typically 80–90% overnight) reduce radiative cooling, while moderate southwesterly winds (10–13 m/s) further limit temperature drops. Official forecasts from PAGASA and international models converge on nighttime lows of 26–27°C under these conditions, consistent with the market’s leading 27°C outcome at 55% implied probability. At the same time, variability in rainfall timing and intensity creates genuine uncertainty: heavier or more prolonged showers could enhance evaporative cooling and nudge the minimum a few degrees lower, supporting the closely matched 21°C-or-below outcome at 47%. Historical September averages (around 24–25°C) are being exceeded due to the current monsoon regime and urban heat-island effects in Metro Manila, but no major tropical cyclone influence is expected in the next 24–48 hours. Updated model runs and PAGASA briefings will likely refine the exact minimum before resolution.