Sydney to cop a drenching after record dry

Mr Taggart said rain would be fairly light in the morning and steadily increase during the day, with heavy rain forecast for peak hour on Thursday afternoon.

"The wettest period for Sydney, the most intense rainfall [will be] from the late afternoon today into sometime tomorrow morning," he said.

The rain comes with the entire state still declared to be in drought.

Australia had its driest September on record last month, with an average rainfall of just 5 millimetres.

While this week's rain is not likely to make a dent in regional rainfall deficits, Mr Taggart said some areas had already had more than 30 millimetres of rain.

"Already we’ve seen some pretty reasonable falls over the south-west of the state. Broken Hill picked up a thunderstorm last night, they've had over 30 millimetres, same with Ivanhoe," he said.

The thunderstorm in Broken Hill followed an incredible red dust storm, with winds up to 109km/h according to the NSW SES.

Mr Taggart said most of the state's thunderstorm activity on Thursday would be in the northern plains region, while the rainfall would be focused on the eastern districts including Sydney, Wollongong and the Central Tablelands.

A hazardous surf warning has been issued for parts of the NSW coast, with hazardous surf and swell conditions expected for the Sydney Coast, Illawarra Coast, Hunter Coast and Macquarie Coast.

"What we're expecting is winds to increase along particularly central parts of the coast later today and into tomorrow," Mr Taggart said.

"That's going to create some pretty choppy seas, so surf conditions will be hazardous particularly tomorrow from Wollongong up to about Port Macquarie."

The bureau warned people should consider staying out of the waters, and rock fishers should avoid rock platforms that are exposed to the ocean.