Saturday sport across Sydney is under threat after a week of persistent wet weather with intermittent showers predicted all day.

More than 30 millimetres of rain fell by Thursday morning, and the start to the weekend is likely to be no better.

"On Friday, Sydney is going to be windier than what we've experienced recently, with south to south-easterly winds, and we will probably still see a number of showers across the day," said Weatherzone meteorologist Rob Sharpe.

"On Saturday we will see a number of showers around, but it will be less windy than on Friday."