"The catchments are really saturated, the dams are full. That makes the rivers really sensitive," Bureau of Meteorology senior meteorologist Jane Golding said.
The SES responded to more than 300 requests for assistance in the past 24 hours, with the majority coming from the central west including Orange, Bathurst and Young.
Nine flood rescues were conducted overnight and into Friday morning, largely for cars in floodwaters.
"A lot of people after many months of lockdown have decided to hit the road. We ask them to be especially vigilant, we don't need you to put yourself at risk and we don't need you to put rescuers at risk as well," SES deputy commissioner Daniel Austin said.
The service is "keeping a very close eye" on communities in the Lachlan River catchments as it has been for some months.
"That catchment particularly has been quite sodden for a long time," Mr Austin said.
"In some places the floodwaters will recede and the ground may dry a little bit. We know the underlying ground is still saturated, so it doesn't take a lot now for any more rainfall to run off."
The rivers may also continue to rise even once the rain stops as water flows into the catchment.
"Don't be fooled by blue sky, it doesn't mean the risk is over... people can get into trouble," Mr Austin said.
The focus has shifted to the southeast of the state with rain predicted over the coming days.
Over a six-hour period beginning at 9am on Friday, the heaviest falls observed were at Perisher Valley (16.6mm), Khancoban (13.6mm) and Forbes (8.8mm).
In the 24 hours before 9am on Friday, Bunnan in the Upper Hunter region recorded 99mm, Mount Palmer recorded 95mm and Merewether in Newcastle recorded 88mm, while Orange received 77mm.
Cessnock (63mm), Lake Macquarie (57mm), Lord Howe Island (51mm), Cowra (49mm), Bathurst (46mm), Goulburn (44mm) and Nowra (39mm) also received significant falls.
The Gwydir River peaked at 6.75m on Thursday afternoon before receding to around 6.11m at Gravesend, causing some minor flooding.
Major flooding is likely on the Lachlan River at Nanami on Saturday night, with moderate flooding expected to impact Cowra earlier in the day at a predicted river height of 11 metres in the morning.
Forbes and Cottons Weir will likely see minor to moderate flooding early next week, from the recent heavy rainfall as well as increased spill from Wyangala Dam southeast of Cowra.
Moderate flooding occurred along the Macquarie River at Bathurst about 2pm, with the river expected to peak about 1am on Saturday near 5.2 metres.
Further downstream at White Rock the river was at almost six metres and rising.
The Belubula River also delivered moderate floods to Canowindra on Friday afternoon
The Willara Crossing over the Paroo River in far west NSW, the Namoi River at Wee Waa, and communities along the Gwydir, Upper Murray, Mitta Mitta, and Snowy Rivers are all expected to experience some minor flooding over the weekend and into next week.
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