By 1.30pm on Thursday the rain gauge at Sydney's Observatory Hill had passed 2200 millimetres recorded this year, breaking the annual rainfall record of 2194mm set in 1950.

With almost three months remaining in 2022 and a third consecutive La Nina declared, further falls mean the new record will be much higher.

After days of driving rain and flooding in inland NSW, a powerful storm system is tracking east with Sydney in for a "dangerous day" on Saturday, Emergency Services Minister Steph Cooke said.

"We know that our catchments are saturated," she said.

"The dams are full and our rivers are already swollen so any extra rainfall - no matter how minor - is likely to exacerbate existing flooding."

The ongoing deluge will heighten flood risks in the coming days across inland and eastern parts of the state, Gabrielle Woodhouse from the Bureau of Meteorology said.

Over the last few days, parts of NSW have already been hit with double to triple the amount of rain they would usually see in a month.

Thunderstorms with isolated supercells will continue in the state's far west on Thursday, bringing the risk of heavy rain, flash flooding, damaging winds and hail.

On Friday a trough and cold front will move across NSW, bringing another widespread band of rain and storms.

Conditions will ease on Saturday morning before a low pressure system forms along the coast in the afternoon, bringing renewed rain in the evening before conditions ease on Sunday.

Renewed and prolonged flooding is continuing in inland NSW at the rivers Namoi, Macquarie, Bogan, Lachlan, Murrumbidgee, Murray, Edward, Culgoa, Birrie, Bokhara, Warrego, Paroo, Barwon and Darling.

Outback towns being monitored closely include Gunnedah, Narrabri, Tamworth, Dubbo, Forbes and Bathurst.

As the weekend continues, the bureau expects to issue further flood warnings on the Hunter River, for Wollombi Brook and at western Sydney's Hawkesbury-Nepean rivers, in Menangle and parts of Penrith.

SES Commissioner Carlene York warned renewed flooding could present different challenges, especially to inland communities.

"This particular event on saturated ground means that things can happen very quickly," she said.

"Don't assume you will get a warning ... it may go straight to an evacuation order."

The Bathurst 1000 is also causing headaches for authorities, with tens of thousands of motorsport fans due to gather at Mount Panorama on the last weekend of school holidays.

"Please don't race to the races," Acting Deputy Police Commissioner Peter Cotter said.

Drivers should be patient and understand they will face delays as some roads will be flooded.

Farmers are also concerned the latest deluge will destroy another crop and graziers have been warned to shelter lambs and sheep.

The bureau has warned livestock is at risk with temperatures set to plunge in the Illawarra, South Coast, Southern Tablelands, South West Slopes, Snowy Mountains and ACT regions.

Australian Associated Press