The Bureau of Meteorology has forecast spring is likely to herald above-average rainfall for people living in the east of Australia, as well as cooler days and warmer nights, after the wettest winter since 2016.

It is already forecasting storms on Tuesday in western NSW. The bad weather will extend eastward on Wednesday with more heavy rain and severe storms expected.

The NSW storm season officially starts on Friday.

Emergency Services Minister David Elliott welcomed the delivery of a deployable Mobile Incident Command Centre to deal with any disasters.

"It can be easily deployed to any location around the state, and further improves the NSW SES' prompt co-ordination and response to natural disasters", Mr Elliott said in a statement on Tuesday.

The SES is also getting new rescue vehicles, including six new 'Unimogs' which can operate in flood waters up to 1.2 metres.

The SES $56.4 million fleet replacement program was on track to deliver 270 vehicles, 124 marine vessels and 95 trailers to some of the state's most flood prone areas.

SES Commissioner Carlene York said her volunteers were preparing for a challenging storm season.

"The difference between now and last year's flooding is our dams are pretty full," she told Sydney radio 2GB on Tuesday.

"We've had a lot of rain over the winter so the ground is pretty saturated ... so it increases the risk of flash flooding."

Australian Associated Press