NSW temperatures are expected to plummet in the coming days and rain will turn into snow as the state gets its first taste of winter.
The Bureau of Meteorology is this week is forecasting rain, wind, snow and thunderstorms as a "really intense" low-pressure system approaches Australia from the polar region.
The bureau's acting NSW manager Jane Golding says the system will move into the west of the state before travelling east over the next two to three days.
"We're expecting that to result in ... vigorous, cool, wintry conditions and blustery winds, some rain, some potential flooding, snow to low levels and also plummeting temperatures and thunderstorms in the mix as well," Ms Golding said in a video on Tuesday.
The highest rainfall totals will be on the western slopes by Wednesday afternoon and evening, she said.
"The more broad, wider areas that see the increased rainfall rates, we're really looking at the central and the southwestern slopes of the ranges," she said.
Warnings are in place for possible minor to moderate flooding for the Tumut, Belubula and Bell rivers and Molong Creek, while a minor flood warning has been issued for the Bogan River.
Ms Golding said the rain was expected to start to turn to snow, first affecting the alpine peaks by late Wednesday before the snow level starts to drop down over the course of Thursday and Friday.
"Places like Orange could see some snow by Thursday," she said.
Ms Golding said there would be a significant drop in temperatures over the next few days.
"This system's bringing with it some really cold air and we should see a marked change from spring-like conditions, which is what we've been seeing in autumn in NSW, to really feeling winter," she said.
BOM meteorologist Adam Morgan said that for some parts of northwest NSW, Thursday would be the coldest April day since the 1960s or 1970s.
Dr Morgan said the winter weather would stay well into the weekend with no relief until early next week.
Australian Associated Press