Meanwhile, traffic accidents were also reported along the Pan Island Expressway, Kallang-Paya Lebar Expressway, Tampines Expressway, and Dunearn Road, according to the LTA's Traffic News Twitter feed.
The rainy conditions are expected to continue for the rest of the morning.
The National Environment Agency (NEA) said on Twitter at 8.42am: "Heavy rain warning: Moderate to heavy thundery showers with gusty wind are expected to continue over many areas".
Videos and photos sent in by ST readers showed water levels reaching near knee-high levels near Upper Changi Road and a car stuck in flood water outside Paya Lebar MRT station.
Mr Mohammad Firdaus, 33, said the junction of Upper Changi Road and Changi South Lane was flooded with water that reached knee levels.
While big lorries and buses could move through the water, “one of the cars looked to be stuck in the water”.
The delivery driver, who has been working at a warehouse nearby for the last nine months, said: “This is the first time I’ve seen such bad flooding.”
Elsewhere, a multi-storey carpark at Block 613A, Ang Mo Kio Avenue 4, was hit too by the heavy downpour, according to Mr Gary Haris, a senior business development manager.
The 43-year-old told ST that he saw water of ankle-high levels rushing down the stairwells.
“I had to roll up my pants, take off my shoes and walk barefooted,” he added