**Forecast models indicate overnight lows of 27–28°C for Singapore on September 20, consistent with the closely matched market odds favoring those outcomes.** Singapore’s equatorial climate produces a narrow diurnal range, where minimum temperatures are shaped by high humidity (typically 70–90%), southeasterly winds, and cloud cover that restricts nighttime radiative cooling. Recent observations and short-range guidance from agencies such as the Met Office and local analyses show partly cloudy to mostly cloudy conditions with scattered showers possible, which tend to hold temperatures above the long-term September average minimum near 25–26°C. Model consensus remains tight, with minor differences arising from exact timing of any cloud breaks or precipitation. Official readings from Changi Airport or the Singapore National Environment Agency will resolve the market once the full 24-hour period ends.