Northeast monsoon flow over northern Taiwan is the dominant driver keeping Taipei's overnight minimum near 22–25°C on September 16, with persistent northeasterly winds, elevated humidity near 70–85%, and variable cloud cover suppressing radiative cooling after sunset. Official Central Weather Administration guidance and multiple model runs show the temperature falling gradually through the evening to a low typically between 22–24°C, while scattered showers or drizzle add further moderation by enhancing latent heat release and reducing clear-sky cooling. The tight clustering of market-implied odds around 22–25°C reflects genuine uncertainty in the precise timing and extent of cloud breaks versus continued moisture advection, with any late-night clearing potentially allowing a dip toward 21–22°C and sustained overcast conditions favoring a higher floor near 24–25°C. Fresh hourly observations from Taipei stations will resolve the outcome as the night progresses.