As 127 coronavirus cases were recorded overnight in Victoria, Mr Park - also Labor's health spokesman - said he had been pushing for the closure over the weekend.

"[Labor leader] Jodi McKay and I called for this closure to be part of the next rollout of measures in an attempt to try and prevent a second wave of the virus impacting NSW and regions like the Illawarra," he said.

"I know that heading to Victoria to visit family, friends or tourist attractions is something that many locals enjoy. But now is not the time. Our region cannot afford both the health and economic consequences that would fall upon us if we were to see transmissions on the rise again."

He urged his constituents to "get in contact with family, friends and loved ones in Victoria and let them know you are thinking of them" but warned that they should "not attempt to go and visit them at this time".

Read more: Premier explains how NSW-Victorian border closure will work

Similarly, Destination Wollongong's Mark Sleigh supported the government's move, as it would be protective for Illawarra small businesses just starting to recover.

"I certainly feel for my colleagues in areas like Sapphire Coast and Eurobodalla, because they've been through bushfires and hard times and rely on visitation from Victorian tourists," he said.

"But for us in Wollongong, if we were to encounter anything like what's happening in Melbourne that would devastating."

The closure will however be a blow to Shellharbour Airport's commercial flight operator Fly Corporate, which has been running a limited number of flights to and from Melbourne since the route was allowed to reopen.

RPT manager Jeff Boyd said it was disappointing to see passenger numbers drop off again, but said he hoped the airline would be able to continue operating for essential travel purposes.

"We're hoping that what we'll now be doing between Melbourne and Shellharbour isn't really different to what we've been doing between Brisbane and Shellharbour,"

"There will still be a level of exemptions, which is what we've had with the Queensland border closure."

"All our passengers will be asked to ensure that they're an exempted person and free to travel, and they will be warned at check in that travelling otherwise could result in extensive fines."

Mr Boyd said he hoped that the reopening of the Queensland border on July 10 would offset some of the lost Melbourne passengers for the company.

Detailing how the closure would work when it comes into force at 11.59pm on Tuesday, Premier Gladys Berejiklian - who previously opposed border closures - said she had no problem changing her views.

"What is happening now in Victoria is very different, all of the cases are from community transmission, this is unprecedented in Australia," she said.

She said police and health officials were already stationed at the state's border, stopping anybody from Victorian hotspots.

"Come midnight tonight, the hotspots will extend to all of Melbourne, and come midnight tomorrow it will be all Victorians," she said.

She said a permit systems was being set up to allow essential workers or anyone who believed they had a reason to travel to apply for an exemption.

She said there would still be some train services and flights available during the closure, "but only for those who have permits and who are returning NSW residents".