Prevailing Inter-Monsoon Conditions To Bring More Thundery Showers In Next Fortnight

Inter-monsoon conditions have set in over Singapore.  Expect more short-duration moderate to heavy thundery showers in second half of April 2018 accompanied with high lightning activity.  A few warm days with maiximum temperature around 35 deg C expected. 

Singapore, 16 April 2018 – Inter-monsoon conditions have set in over Singapore and the surrounding region, and are forecast to persist for the rest of April and extend into May 2018. During this period, the low level winds are generally light and variable in direction.

2          The inter-monsoon period is characterised by warm weather and moderate to heavy thundery showers falling mostly in the afternoon and occasionally extending into the evening. Typically, thunderstorms during the inter-monsoon period are more intense than other times of the year. This is due to strong solar heating of land areas as the sun is closer to the Equator. April is climatologically the month with one of the highest number of lightning occurrences.

3          The second fortnight of April 2018 is forecast to be wetter than the first fortnight, with short-duration moderate to heavy thundery showers expected mainly in the afternoon on seven to nine days. Also in this fortnight, Sumatra squalls moving from the Strait of Malacca to the South China Sea could bring widespread thundery showers accompanied with gusty winds over Singapore on two or three days between the predawn hours and early morning. With the expected wetter conditions in the coming fortnight, the overall rainfall for April 2018 is likely to be near average.

4          Climatologically, April is one of the warmest months of the year. In the second half of April 2018, a few warm days can be expected. On most days, the daily temperatures are expected to range between 24°C and 34°C, and could reach a high of around 35°C on a few days. With expected widespread rain on a few days in the coming fortnight, the minimum temperature on these days could reach a low of around 23°C.

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

REVIEW (1 – 15 April 2018)

6          The Northeast Monsoon conditions gave way to the inter-monsoon conditions in the first half of April 2018. The prevailing low level winds over Singapore became light and variable in direction having been predominantly blowing from the northeast or northwest for the past few months.

7          In the first half of April 2018, the strong daytime heating of the land area coupled with generally light winds during the day were conducive conditions for the development of thundery showers over Singapore. Most of the thundery showers fell in the afternoon and were more intense in the second week of April 2018. Rainfall was heaviest on 7 April 2018 around the MacRitchie Reservoir area where the daily total rainfall recorded was 138mm.

8          There were some warm days during the first fortnight of April 2018. The daily maximum temperature ranged between 33.2°C and 34.9°C, particularly over the northern and western parts of Singapore. The highest value of 34.9°C was recorded at Khatib in Yishun. The daily minimum temperature ranged from 22.5°C to 25.5°C.

9         About two-thirds of Singapore received below-normal rainfall in the first fortnight of April 2018. The lowest rainfall of 20.4mm (73% below average) was recorded at Changi. Rainfall was highest around Jurong where 219.8mm (66% above average) was recorded.


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

Mean daily maximum temperature 32.3 °C
Mean daily minimum temperature 25.0 °C
Mean monthly temperature 28.0 °C
Mean rainfall for the month 154.8 mm
Mean number of rain days 14
Highest monthly mean daily maximum temperature 33.9 °C (1983)
Lowest monthly mean daily minimum temperature 23.9 °C (1982)
Highest monthly rainfall 311.6 mm (2000)
Lowest monthly rainfall 43.1 mm (1983)