A torrential downpour lashed Sydney and other parts of NSW on Tuesday afternoon, with more expected throughout the week as the humidity hits 90 per cent.

The Bureau of Meteorology issued a severe thunderstorm warning on Tuesday, forecasting heavy rainfall for residents in parts of the Blue Mountains-Hawkesbury region, Gosford-Wyong and western Sydney.

“The Bureau of Meteorology warns that, at 1.40pm, severe thunderstorms were detected on the weather radar near Mona Vale and waters off Bondi Beach,” the weather bureau said in a warning.

“They are forecast to affect Hornsby, Sydney City, Sydney Airport, Sydney Olympic Park and the Sydney Harbour Bridge by 2.10pm and Parramatta, Richmond and Riverstone by 2.40 pm.”

The heavy rain could lead to flash flooding in some areas.

Tweet from @BOM_NSW

By early Tuesday afternoon, parts of western Sydney had already received 65 millimetres of rain since 9am.

Wyong, on the NSW central coast, had  143 millimetres in the same time frame.

Storms and heavy rain would last for several days, the BoM said.

There was also a more general severe thunderstorm warning for the Sydney metropolitan, upper western and parts of the mid-north coast, Hunter, Illawarra, central tablelands, north-west slopes and plains and lower western districts.

– with AAP