Wet weather conditions expected in the first fortnight of 2018. Short-duration thundery showers between the afternoon and evening on some days, and occasionally windy conditions with widespread moderate to heavy rain and cool temperatures on a few days due to a monsoon surge.
Singapore, 2 January 2018 – The prevailing Northeast Monsoon season is forecast to continue into the first fortnight of 2018. During the next two weeks, the low level winds over Singapore and the surrounding vicinity are expected to blow mainly from the northeast or northwest.
2 The wet weather conditions experienced in Singapore in the last few days of December 2017 are expected to continue in the first half of January 2018. During the two weeks, moderate to heavy thundery showers are forecast in the afternoon on six to eight days. On a few of these days, the thundery showers could extend into the early evening. A monsoon surge could affect the South China Sea and the surrounding region in the latter half of the fortnight. The surge is expected to bring a few days of occasionally windy conditions with widespread moderate to heavy rain and cooler temperatures to Singapore. Rainfall for the first half of January 2018 is expected to be above normal.
3 During the first fortnight of January 2018, slightly cooler night-time minimum temperatures of 23°C to 24°C can be expected. The maximum day-time temperatures are likely to range between 31°C and 33°C.
REVIEW (1 – 31 December 2017)
5 Northeast Monsoon conditions prevailed over Singapore and the surrounding region in December 2017, and the low level winds were predominantly from the northeast or northwest.
6 In early December 2017, strong solar heating of land areas coupled with convergence of winds brought moderate to heavy thundery showers over Singapore in the afternoon and early evening on several days. In the third week of the month, the presence of two consecutive tropical storms in the South China Sea had an influence on the weather and wind conditions in the surrounding region. Winds over Singapore shifted to blow from the southwest and the passage of Sumatra squalls across the island brought widespread thundery showers in the predawn hours and morning on a few days. In the last week of the month, a monsoon surge on 30-31 December 2017 brought overcast and occasionally windy conditions with periods of widespread moderate to heavy rain to Singapore. The highest total daily rainfall recorded in December 2017 was 149.6mm around the Buona Vista area on 31 December 2017.
7 In December 2017, the daily maximum temperatures ranged between 26.8°C and 35.1°C, and the daily minimum temperatures ranged between 22.3°C and 25.6°C. At the Changi climate station, the daily maximum temperature of 33.5°C recorded on 1 December 2017 is the second highest daily maximum temperature on record for December, 1°C lower than the highest record set on 12 December 2010. In addition, the mean monthly temperature of 27.1°C for December 2017 is 0.7°C above the long-term mean for December.
8 About half of Singapore received above normal rainfall in December 2017. The highest rainfall of 502.4mm (65% above average) was recorded around the Seletar area. Rainfall was lowest around the Bukit Panjang area where 211.6mm (28% below average) was recorded.
 A monsoon surge refers to the strengthening of northeasterly winds blowing from a strong high-pressure system over the northern Asian continent toward the South China Sea, bringing periods of prolonged widespread rain and windy conditions to the surrounding region including Singapore and Peninsular Malaysia. (Further information is available at www.weather.gov.sg/learn_weather_systems/)
CLIMATE STATION STATISTICS FOR JANUARY (Climatological reference period: 1981 – 2010)
|Mean daily maximum temperature||30.4 °C|
|Mean daily minimum temperature||23.9 °C|
|Mean monthly temperature||26.5 °C|
|Mean rainfall for the month||234.6 mm|
|Mean number of rain days||13|
|Highest monthly mean daily maximum temperature||31.8 °C (1998)|
|Lowest monthly mean daily minimum temperature||22.6 °C (1981, 1982)|
|Highest monthly rainfall||600.9 mm (2004)|
|Lowest monthly rainfall||15.4 mm (1997)|