Southwest Monsoon Conditions to Persist For Rest of September 2017

Thundery showers provide some respite to warm days

Singapore, 15 September 2017 – The Southwest Monsoon season has been prevailing since June 2017 and is forecast to persist for the rest of the month. The low level winds over Singapore and the surrounding region are forecast to blow mostly from the southeast or southwest. On some mornings the winds are expected to be generally light and variable in direction.

2          In the second half of September 2017, Singapore can expect thundery showers on six to eight days, mostly in the late morning and early afternoon. In addition, on two or three days in the coming fortnight, widespread thundery showers accompanied by occasional gusty winds, arising from the passage of Sumatra squalls can be expected between the pre-dawn hours and morning. The total rainfall for September 2017 is expected to be slightly above normal.

3          On most days during the fortnight, the daily temperature is expected to range between 24°C and 33°C. On a few days, it is likely to be warm with the daily maximum temperature reaching a high of around 34°C. The lowest daily minimum temperature in the next two weeks could fall to around 23°C on one or two rainy days.

4          For updates of the daily weather forecast, please visit our MSS website (, NEA website (, or download the myENV app, or the MSS’ Weather@SG app.

Review: 1 – 14 September 2017

5          Southwest Monsoon conditions prevailed over Singapore and the surrounding region in the first fortnight of September 2017. The low level winds during the two weeks were predominantly from the southeast or south.

6         In the first half of September 2017, Singapore experienced thundery showers mostly in the late morning and early afternoon due to strong solar heating of land areas coupled with convergence of winds over Singapore and the surrounding vicinity. On a few days, the thundery showers were due to the passage of a Sumatra squall that moved over Singapore in the predawn and early morning. The heaviest daily rainfall of 94mm was recorded on 10 September 2017 around the Sungei Kadut area.

7          There were a few warm days during the fortnight where the daily maximum temperature reached a high of between 34.1°C and 34.4°C.  The lowest daily minimum temperature recorded ranged between 22.9°C and 23.5°C. At the Changi climate station, the mean monthly temperature recorded for the first fortnight of September 2017 was 28.2°C, which is 0.6°C higher than the long-term mean temperature for September.

8          Most parts of Singapore received below-normal rainfall in the first fortnight of September 2017. The lowest rainfall of 24.1mm (69% below average) was recorded around the Paya Lebar area. Rainfall was highest around the Bukit Panjang area where 146.4mm (53% above average) was recorded.


CLIMATE STATION STATISTICS FOR SEPTEMBER (Climatological reference period: 1981 – 2010)

Mean daily maximum temperature 31.4 °C
Mean daily minimum temperature 24.8 °C
Mean monthly temperature 27.6 °C
Mean rainfall for the month 156.5 mm
Mean number of rain days 13
Highest monthly mean daily maximum temperature 32.2 °C (1997)
Lowest monthly mean daily minimum temperature 23.6 °C (1986)
Highest monthly rainfall 440.4 mm (1988)
Lowest monthly rainfall 23.7 mm (1994)