Singapore's tropical climate features minimal seasonal temperature swings, with September under prevailing southwest monsoon conditions typically producing overnight lows near the long-term average of 25°C amid high humidity and frequent thundery showers. Current forecasts from multiple models converge on a minimum around 26°C for September 18, supported by recent observations of nighttime readings staying above 27°C in the first half of the month and no significant cooling from cloud cover or rainfall. Trader consensus at 85% for 26°C as the lowest temperature aligns with this stable pattern and official guidance projecting minimums above 27°C on many nights, while lower outcomes remain unlikely without an atypical surge in convective activity or measurement anomaly at the resolving station.