Severe weather posing a risk of flash and riverine flooding is forecast for much of western NSW as emergency responders prepare for more rescues in the final days of school holidays.
"We're looking at around a month or more worth of rain, particularly across inland areas in NSW," Gabrielle Woodhouse from the Bureau of Meteorology said on Tuesday.
Two significant weather systems will bring thunderstorms and high rainfall totals of up to 50 to 80mm across NSW in the coming days, with heightened flood risk across inland parts of the state.
"We'll start to see more of a flash flood risk as well as riverine flood risk over the coming days," Ms Woodhouse said.
"There is a lot of rain and ... it's falling on very very wet catchments."
Rain and thunderstorms hit inland NSW on Tuesday, with a severe weather warning for heavy falls and a risk of flash-flooding covering much of the state's west, from Nyngan in the central north, to Deniliquin near the Victorian border, through to Broken Hill in the central west.
The weather system will shift on Tuesday afternoon bringing widespread, heavy falls east through to Wednesday before weakening on Thursday as it moves south.
A second system will bring more rain on Friday, with a widespread deluge forecast for the western slopes and ranges, continuing to the coast on the weekend.
The drenching will not be as severe for residents of the NSW north coast, but more severe rainfall could develop along with high winds and heavy waves as the low pressure system develops towards the weekend.
The SES is concentrating on key communities as it expects to cop flooding in western and central NSW towns including Gunnedah, Wee Waa and Warren this week.
Nyngan, about one hour from Warren, is also being monitored closely, SES Commissioner Carlene York said.
Major rivers of concern include the Namoi, the Darling, Culgoa, Bogan and Barwon rivers, and anyone travelling around those areas needs to be prepared.
A stranded driver had to be rescued by SES volunteers on Monday after trying to drive across a flooded roadway, Ms York said.
As the school holidays come to an end this weekend, she urged people to drive with care, and not to drive across flooded roadways.
