Singapore residents should prepare for increased rainfall in the second half of September 2026, with the Meteorological Service Singapore forecasting regular afternoon thundery showers. While daytime temperatures will remain warm, reaching up to 35°C on some days, the approaching wet weather may provide relief from ongoing regional haze.
Monsoon Conditions and the Forecast for Late September
Keep umbrellas ready as more rain is expected in Singapore during the second fortnight of the month. According to the Meteorological Service Singapore (MSS), short and thundery showers will develop between the late morning and afternoon across parts of the island on most days. Widespread moderate to heavy thundery showers can also be expected over the island on one or two days, the Met Service said. Overall, the total rainfall for the second fortnight of September is forecast to be near the long-term average across most parts of the island.
The Met Service said the south-west monsoon conditions prevailing over Singapore and the surrounding region are expected to continue in the coming fortnight, with winds blowing mainly from the south-east or south-west. Singapore’s climate is defined by two primary monsoon seasons, and the Southwest Monsoon from June to September is dominated by southeasterly to southerly winds, with frequent Sumatra squalls
occurring during the pre-dawn and morning hours bringing gusty winds and short-duration thundery showers.
Persistent Heat and Humidity
The shift in weather does not mean an end to the tropical heat. Daily maximum temperatures are likely to range between 33 deg C and 34 deg C on most days, and could reach 35 deg C on a few days. Nighttime will offer little cooling comfort.
Warm and humid conditions can still be expected on some nights, with minimum temperatures remaining above 27 deg C. This humid pattern mirrors conditions observed throughout the year in Singapore, where relative humidity often exceeds 90 per cent in the early morning and drops to around 60 per cent in the mid-afternoon on dry days. Singapore, located just north of the equator, experiences a tropical rainforest climate characterized by consistent warmth, high humidity, and abundant rainfall throughout the year, with an average annual rainfall of approximately 2,340 mm.
Reviewing the Dry Start to September
The wetter outlook contrasts sharply with the first half of the month, which proved unusually dry. In its review of the first half of September, the Met Service said the weather was mostly dry, with brief, thundery showers occurring over parts of Singapore on some days. The rainfall recorded for the fortnight was well below average, with the area around Changi registering rainfall of about 98 per cent below average.
It was mostly warm in the first fortnight of September. Daily maximum temperatures exceeded 34 deg C on 12 occasions, with the highest at 35.3 deg C recorded in Sembawang on Sept 9. Nights stayed warm, with minimum temperatures remaining above 27 deg C across many parts of the island.
The dry spell broke when regional wind convergence brought moderate to heavy thundery showers over many parts of the island during the late morning and afternoon of Sept 11. The mercury dipped to a low of 22.4 deg C in Scotts Road that day at 3.51pm, according to the Met Service’s website. MSS stated: The daily total rainfall of 105mm recorded around Scotts Road area that day was the highest rainfall recorded for the first half of September 2026.
Flash Flood Risks and Haze Relief
Heavy rain was expected over many areas of Singapore on Thursday, Sept 10 morning, with the National Environment Agency (NEA) issuing a weather update at 7.55am stating that moderate to heavy thundery showers with gusty winds were forecast to last till 9.30am. Separately, Singapore’s national water agency PUB announced on its Telegram channel that the risk of flash floods existed at Jalan Boon Lay — from International Road to Enterprise Road, and the junction of Pesawat Drive and Jurong Port Road, which are located in Jurong West.
Unhealthy levels of haze in 2026 were first detected in central Singapore on Sept 4, when the 24-hour PSI reading crossed the threshold reading of 101, and hazy conditions have prevailed across Singapore since then. Since Sept 4, the National Environment Agency (NEA) has begun publishing Daily Haze Advisories (DHA).
The air quality in Singapore improved on Sept 16, after unhealthy levels of pollutants were recorded all country-wide the day before, while previously bouts of unhealthy haze were detected only in parts of the country. The improvement came as showers continued over parts of Kalimantan in neighbouring Indonesia, the National Environment Agency (NEA) said in its daily haze advisory on Sept 16, though some smoke haze was observed to drift from the southern parts of Sumatra towards Singapore. As at 5.30pm on Sept 16, the 24-hour Pollutant Standards Index (PSI) readings in all five regions of the island stayed in the moderate range — logging values of between 51 and 100. NEA stated at about 6pm on Sept 16 that air quality in Singapore for the next 24 hours was forecast to be in the moderate to low-unhealthy range as dry conditions are expected to continue over southern and central Sumatra, as well as the southern parts of Kalimantan, where forest fires have raged for weeks.
