While not much rain fell this morning, we could receive around half our average March rainfall this afternoon, the Bureau of Meteorology says.
The bureau has forecast between 25 and 70 millimetres, expected to affect mostly Sydney's coastal suburbs.
The falls are likely to hit in the afternoon and evening with the chance of thunderstorms, bureau forecaster Zhi-Weng Chua said.
"It will ramp up this afternoon and probably ease off tomorrow morning," he said.
"If you had to give a more likely amount, it would be closer towards the lower end, maybe 20 to 40, but 70 millimetres is still a possibility."
The average rainfall for March recorded at Observatory Hill is 130.8 millimetres. The highest rainfall total for March is 521.4 millimetres recorded in 1942, while the lowest rainfall for March was a mere 8.4 millimetres in 1964.
Duty bureau meteorologist Dmitriy Danchuk said the chance of Sydney receiving 70 millimetres was 25 per cent, while the chance of 25 millimetres was 50 per cent.
Parts of Sydney received almost 50 millimetres on Wednesday, Mr Danchuk said.
"In the city we had just six millimetres, but the far northern beaches had falls of between 20 and 50 millimetres," he said.
Mr Chua said the wet weather would continue over the coming days.
"There’s still going to be lingering showers and there’s still the possibility that the weekend could be wet," he said.
"Early parts of next week could be wet as well."
Sydney is forecast to receive between 15 and 45 millimetres on Friday, with a chance of a thunderstorm in the morning and afternoon.