Singapore September Weather: Key Characteristics
Singapore’s September weather is shaped by the Southwest Monsoon, a seasonal wind pattern that brings consistent hot, humid conditions and scattered thunderstorms. This month is part of the island’s tropical rainforest climate, where temperature and humidity remain high yearround, but rainfall patterns are influenced by monsoon dynamics.
Temperature: Hot and Stable
Daily temperatures in September hover between 25°C (77°F) and 32°C (90°F). Daytime highs often feel more intense due to high humidity, with feelslike temperatures sometimes reaching up to 45°C (113°F). Nighttime lows rarely drop below 21°C (70°F), ensuring warm conditions throughout the day and night. These temperature ranges are consistent with Singapore’s tropical profile, where extremes are rare.
Rainfall: Frequent Thunderstorms, Moderate Totals
September is part of Singapore’s wetter season, with 13–19 rainy days per month (accounting for 40–60% of the month). Rain typically falls in short, heavy afternoon thunderstorms, driven by convective activity and Sumatra squalls (localized wind surges from Indonesia). While daily rainfall can be intense (up to 50mm or 2 inches in some areas), monthly totals average around 125mm (4.9 inches)—slightly higher than August but less than the peak rainy months of November–January. Geographical variations exist: inland areas like Punggol may see more rainfall (up to 34mm per rain day), while coastal or elevated spots like Bukit Timah receive slightly less (around 25mm per rain day).
Humidity: Very High, Typical of Tropical Climates
Relative humidity in September averages 81%, with daily fluctuations between 62% (early morning) and 94% (late afternoon). This persistent humidity amplifies the perception of heat, making the weather feel muggy even when temperatures are moderate. The high humidity also contributes to the rapid development of thunderstorms in the afternoon.
Wind: Light to Moderate, Limited Relief
Winds during September are generally light to moderate, averaging 4.7 mph (7.6 kph). The Southwest Monsoon brings winds from the southeast or southwest, which provide minimal cooling relief due to the island’s proximity to the equator. These winds are strong enough to disperse some moisture but not enough to significantly lower temperatures or reduce humidity.
Key Weather Impacts
The combination of heat, humidity, and frequent thunderstorms makes September a challenging month for outdoor activities. However, it is also a low tourist season, with fewer crowds and slightly lower prices for accommodation and transport. Visitors are advised to pack lightweight, breathable clothing, umbrellas or rain jackets (for sudden showers), and sun protection (sunglasses, hats, sunscreen) to stay comfortable.