More Thundery Showers Expected in The First Half of Nov 2017

Expect more afternoon thundery showers in 1st half of Nov’17. Showers could extend into the evening on a few days.

Singapore, 1 November 2017 – Singapore and the surrounding region are experiencing inter-monsoon conditions which are expected to prevail in November 2017. The inter-monsoon period is characterised by more rainfall and light winds that are variable in direction. Climatologically, lightning activity during the inter-monsoon period is highest during the year.

2          November is normally the second wettest month of the year after December. For the first half of November 2017, short-duration moderate to heavy thundery showers are forecast mostly in the afternoon on six or eight days. On a few of these days, the thundery showers could extend into the evening, and high lightning activity can be expected. On two or three days during the first fortnight of the month, Sumatra squalls moving eastward across Singapore towards the South China Sea could bring widespread thundery showers accompanied by gusty winds to the island between the predawn hours and early morning. Rainfall for the first fortnight of November 2017 is expected to be above normal.

3          In the first half of November 2017, the daily temperature on most days is forecast to range between 24°C and 33°C. On a few days, the daily maximum temperature could reach a high of 34°C, in particular on fine weather days when there are few clouds in the sky and winds that are light.

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

REVIEW (1 – 31 October 2017)

5          Southwest Monsoon conditions with low level winds blowing from the southeast or southwest prevailed over Singapore and the surrounding region in the first half of October 2017. In the third week of the month, the Southwest Monsoon eased to give way to inter-monsoon conditions where winds weakened to become light and variable in direction.

6          Except for the third week of the month, it was relatively wet in October 2017. The dry and warm conditions in the third week of October 2017 was due to stable atmospheric conditions as warm and dry air prevailed over Singapore and the surrounding region. During the month, most of the thundery showers fell in the late morning and afternoon, and on a few days, extended into the evening. The thundery showers were due to strong solar heating of land areas coupled with the convergence of winds over Singapore and the surrounding vicinity. The occurrence of Sumatra squalls on several days also brought moderate to heavy thundery showers to many parts of Singapore between midnight and early morning. The heaviest daily rainfall recorded during the period was 129.8mm around Tuas on 12 October 2017. There were 21 rain days1 in October 2017, three days more than the long term mean for October. This ties with the highest number of rain days for October recorded in 1985 and 2003.

7          The daily temperature in October 2017 ranged between 22.6°C and 35.3°C. During the week of 16 October 2017, when conditions were warm and dry, there were five days when the daily maximum temperature was more than 34°C. At the Changi climate station, the highest daily maximum temperature recorded was 34.6°C on 18 October 2017. This ties with the highest daily maximum temperature ever recorded at our climate station in October (in 2002 and 2016). The mean monthly temperature recorded for October 2017 was 28.1°C, which is 0.5°C warmer than the long-term mean for October.

8          About half of Singapore received above normal rainfall in October 2017. The highest rainfall of 286.4mm (33% above average) was recorded around MacRitchie Reservoir. Rainfall was lowest around Admiralty where 114.8mm (46% below average) was recorded.

1A rain day is defined as a day where 0.2mm or more of rain was recorded.


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

Mean daily maximum temperature 31.1 °C
Mean daily minimum temperature 24.3 °C
Mean monthly temperature 27.0 °C
Mean rainfall for the month 258.5 mm
Mean number of rain days 18
Highest monthly mean daily maximum temperature 32.0 °C (1997)
Lowest monthly mean daily minimum temperature 23.6 °C (1981, 1983, 1991)
Highest monthly rainfall 508.4 mm (1989)
Lowest monthly rainfall 53.5 mm (1981)