Inter-Monsoon Conditions to set in by End-October 2018

Singapore, 16 October 2018 – In the second fortnight of October 2018, the low level southeasterly or southwesterly winds are forecast to gradually weaken to become light and variable in direction by the last week of the month. The change in conditions would signal the cessation of the Southwest Monsoon season and the start of the inter-monsoon period.

2         The inter-monsoon conditions are forecast to last through November 2018, and the period is characterised by warm weather and thunderstorms that can at times be intense. During the inter-monsoon months, lightning activity tends to be higher than other months of the year.

3         The second fortnight of October 2018 is not expected to be as wet as the first fortnight of the month. For the rest of the month, localised short-duration thundery showers due to strong day-time heating of land areas coupled with convergence of winds in the surrounding vicinity, are expected in the late morning and afternoon on five to seven days. On one or two days, widespread thundery showers accompanied with gusty winds can be expected over Singapore between predawn hours and early morning, arising from Sumatra squalls moving eastwards from the Strait of Malacca to the South China Sea. Overall, the rainfall for October 2018 is expected to be above normal over most parts of Singapore.

4         In the second half of October 2018, the daily temperatures on most days are forecast to range between 25°C and 33°C. Warm conditions with maximum day-time temperatures that could reach a high of around 35°C in the afternoon can be expected on a few days when there is little or no rainfall.

5         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 – 15 October 2018)

6         Southwest Monsoon conditions prevailed in the first fortnight of October 2018 with low level winds blowing mainly from the east-southeast or south-southwest.

7         For most days in the first week of the month, stable atmospheric conditions in the region brought dry and warm weather over Singapore and the surrounding region. In contrast, the region experienced rainy conditions in the second week of October 2018. The wet weather over Singapore and the surrounding region was due to the presence of persistent easterly winds bringing moisture from the Tropical Central Pacific Ocean to the southern Southeast Asia region between 6 and 14 October 2018. The total rainfall of 109.8mm recorded at Sentosa on 9 October 2018 was the highest daily rainfall recorded in the first fortnight of October 2018.

8         The daily temperature recorded in the first fortnight of October 2018 ranged between 22.5°C and 35.6°C. It was dry and warm on most days in the first week of the month, and the daily maximum temperature recorded that week was around 35°C on a few days. The highest daily maximum temperature of 35.6°C was recorded on 5 October 2018 at Marina Barrage. The rainy weather in the second week of October 2018 brought relatively cool conditions and some respite to the warm conditions experienced the week before. On 13 and 14 October 2018, with overcast skies and several spells of rain showers throughout the day, the daily maximum temperature recorded on both days fell to 30.1°C and 28.4°C respectively. The lowest daily minimum temperature recorded during the rainy period (6 – 14 October 2018) ranged between 22.5°C and 23.6°C. The lowest daily minimum temperature of 22.5°C was recorded around the Changi area on 12 October 2018.

9         Rainfall during the first fortnight of October 2018 was above normal across the island. Highest rainfall of 224.0 mm (170% above average) was recorded around the Sentosa area. Areas in the northeastern part of Singapore around Changi, Pasir Ris and Seletar received rainfall ranging from 162 mm to 198 mm (90 to 166% above the average). Areas around Ulu Pandan received the lowest rainfall of 99.6 mm (9% below the average).


(Climatological reference period: 1981 – 2010)

Mean daily maximum temperature 31.7 °C
Mean daily minimum temperature 24.7 °C
Mean monthly temperature 27.6 °C
Mean rainfall for the month 154.6 mm
Mean number of rain days 15
Highest monthly mean daily maximum temperature 33.0 °C (2002)
Lowest monthly mean daily minimum temperature 23.8 °C (1982)
Highest monthly rainfall 351.4 mm (2003)
Lowest monthly rainfall 10.8 mm (2002)