Recent official forecasts from Taiwan's Central Weather Bureau and international models converge on a September 21 overnight low in Taipei near 22–24 °C under northeast monsoon flow, partly cloudy skies, and light easterly winds that limit daytime heating while permitting moderate nocturnal radiative cooling. This range aligns with the tightly clustered market-implied odds around 22–25 °C. Historical September minima in the city average 23–24 °C, and current guidance shows no tropical systems or frontal passages to drive sharper drops or spikes. Traders appear to weigh the small model spread in boundary-layer humidity and wind speed—variables that can shift the minimum by 1–2 °C—against the stable large-scale pattern, producing near-even probabilities across the central outcomes ahead of final overnight observations.