Callers to the MediaCorp hotline reported flooding in areas such as Cuscaden Road, Hillcrest Road, Eng Neo Avenue, Sennett Estate near Potong Pasir, MacPherson, Toa Payoh, and Balestier.
They also reported fallen trees caused by the downpour and gusty wind.
Parts of Orchard Road were also reported to be affected by flooding, especially along the stretch of Tanglin Mall.
Both Tanglin Mall and Forum Shopping Mall were affected with many stores having to close temporarily.
MediaCorp understands that water levels were about ankle-deep.
The ground level and basement of the malls were the hardest hit.
Some shoppers had problems getting to their cars, with most having to wait until they were given the green light to go to the carpark.
When MediaCorp visited the malls, store owners and employees there said that they had been cleaning up for more than two hours.
Earlier, two lanes along Bukit Timah Road and the slip road of the Kranji Expressway towards Woodlands were impassable to traffic.
National water agency PUB said various areas in the central and western parts of Singapore were hit by flooding. It advised the public to be careful on these roads.
Drivers were advised to avoid these roads.
In a statement at 12.15pm, PUB said the flash floods reported earlier along Bukit Timah Road (the stretch from Blackmore Road to Maplewood Road) and Dunearn Road (from Rifle Range Road to Yarwood Road) as well as at Orchard Road (Cuscaden Road - at the Tanglin/Tomlinson Road junction and Tanglin/Napir Road junction) had subsided.
These roads are now passable to traffic.
In Bukit Timah, the management committee of Tessarina condominium told MediaCorp that residents were alerted by a siren on Sunday morning when the Bukit Timah canal burst its banks.
Many drove their cars out of the basement to higher grounds.
The flood barrier at the condominium was also activated as a preventive measure.
The condominium was one of the places badly affected by previous floods.