Emergency services were called to the Coopers Creek Canal about 8.20am on Tuesday to reports a body had been sighted in the water, near Hopkins Street in Constitution Hill.
Earlier, police had appealed for help to locate a missing mother and her son after their Mazda 3 was found in a stormwater canal at Wentworthville about 4:30 pm Monday.
Authorities have been unable to locate the car’s owner, a 67-year-old woman, or her 34-year-old son, despite their personal belongings discovered in the submerged vehicle.
Police are expected to make an announcement once the bodies have been identified.
It comes as the state's emergency services have ordered residents in parts of Penrith and Lower Portland to evacuate.
While Sydney and the Hawkesbury are on alert for a "very dangerous" thunderstorm.
"Intense rainfall with this very dangerous thunderstorm which is slow moving," the Bureau of Meteorology (BOM) has issued.
"Likely to see significant flash flooding, possibly landslips."
BOM has also warned of major flooding in the Kempsey CBD and surrounding areas on the NSW mid-north coast from Tuesday afternoon.
Residents in Hornsby, Parramatta and Richmond have also been alerted to severe weather with "very heavy" rain and thunderstorms.
The weather bureau expects floods in the next 24-48 hours to hit along the NSW coastline, declaring the "significant" weather event will run until Thursday.
Those in Kempsey, Coroki, Georges River and residents along the Hawkesbury-Nepean River, as well as Shoalhaven, St Georges Basin and Sussex Inlet are in today's firing line.
Evacuation Warnings:
- Parts of Penrith
- Parts of Lower Portland
- Parts of Regentville
- Parts of Cranebrook - Waterside Estate
- Parts of Cranebrook (multiple areas)
Evacuation Orders:
- Low lying areas of Sussex Inlet
Parts of Camden, including:
- Exeter Street west of John Street and Milford Road, Camden West
- Mitchell Street
- Elizabeth Street
- Argyle Street
- Lerida Street
- Edward Street
For a full list of evacuation warnings and orders visit the NSW SES website
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