SINGAPORE: Temperatures dropped to a low of 21.1°C on Saturday (Jan 2) as cool and rainy weather from a monsoon surge continued on from Friday, the National Environment Agency (NEA) said.
In a Facebook post, NEA said widespread continuous rain and some thundery showers were expected on Saturday before easing at night.
Similar conditions are forecast for the next few days as well.
As of 7pm on Saturday, the highest total rainfall recorded was 210.6mm at Changi.
"This exceeds the second-highest ever recorded daily rainfall of 194.4mm for January at the Changi climate station (the record high for January is 216.2mm)," said NEA.
The mercury dropped to a low of 21.1°C at Newton in the afternoon, added the agency in an update. This was revised down from 21.3°C earlier in the day.
On New Year's Day, Simei recorded the most rainfall at 147.3mm, while the lowest temperature was 21.2°C, also at Newton.
According to national water agency PUB, as of noon on Saturday, the highest total amount of rainfall recorded at Changi since Friday was 318.6mm, which is more than the equivalent of the average monthly rainfall for January (238.3mm).
"This is the first monsoon surge occurrence in the current northeast monsoon season," NEA said.
It refers to a strengthening of winds over the South China Sea, causing extensive rainclouds to form over the surrounding region.
Typically, there are two to three surge occurrences during the season, NEA said.
"The relatively low temperatures experienced at present are primarily due to the cool air masses associated with the monsoon surges", said Dr Matthias Roth, Professor of Urban Climatology at the National University of Singapore.
An additional factor is reduced incoming solar radiation as sustained, extensive cloud cover prevents the sun from heating up the air near the ground, he said.
However, the prolonged rain spells should disappear once the dry phase arrives in February, Dr Roth added.
"Weak La Nina conditions are predicted to last until May and may result in slightly above average rainfall," he said.
"Thereafter conditions should return back to normal for the rest of the year."
PUB noted that it issued flood risk warnings for several locations, including Lorong Halus, Pasir Ris Farmway 3, Jalan Seaview, Mountbatten Road and the junction of Bedok Road and Upper Changi Road East, when heavy rain caused water levels in the drains and canals to exceed 90 per cent capacity.
"Over the two days, PUB’s quick response teams were deployed to direct traffic and render assistance to residents in the areas stated above to protect them from flood risk," the agency said, adding that its officers helped residents in Mountbatten and Jalan Seaview install inflatable flood bags to protect their homes.
According to a weather advisory by the Meteorological Service Singapore on Thursday, moderate thundery showers and windy conditions are expected in the afternoon in the first two weeks of 2021.
On a few days, large-scale convergence of winds in the region could bring heavy and widespread thundery showers over the country.
The unusually cooler conditions can be attributed to both man-made climate change and a natural "stretch of bad luck", says Professor Benjamin P Horton, Director of the Earth Observatory of Singapore at the Nanyang Technological University.
"Predicted climate change will significantly increase water-related risks, especially increasingly frequent and intense extreme rainfall events," he said.
"The Earth is getting warmer, with significantly more moisture in the atmosphere. As the atmosphere gets warmer, it can hold more moisture. The intensity of downpours (and therefore the risk of floods) depends in part on how much water the air can hold at a given time."
The highest recorded daily total rainfall and lowest recorded temperature for the month of January in the past 10 years was 238.2mm at Pulau Ubin on Jan 30, 2011 and 20.1°C at Tengah on Jan 31, 2014.
For Sunday, NEA said it is expected to be cloudy in the morning, with thundery showers in the afternoon. The temperature is forecast to range between 22°C and 31°C.