The Bureau of Meteorology has predicted showers on Sunday afternoon and evening would lead to a 90 per cent chance of up to 30mm of rain on Monday.

Although it's still too early to tell whether this weather pattern is the precursor to the development of a so-called east coast low.

The previous east coast low which formed back in early February brought lashing rain and gale-force winds from the Queensland border to the far NSW South Coast.

It will be remembered as the intense, key rain event which effectively extinguished the South Coast and Namadgi bushfires and put an end to the long, awful fire-laden summer across NSW.

Meteorologist Helen Kirkup said the combination of a broad low pressure trough and upper level atmospheric instability over inland NSW will bring a significant change in existing conditions toward the end of the weekend but for a full-blown east coast low to develop "it requires a combination of factors to line up together".

"However, it's not out of the question with this system," she said.

The trough will move slowly east through the weekend and is expected to dump a hefty amount of rain on the ACT on the latter part of its journey through, with light winds then becoming southerly in direction.

She said as the trough reached the coast and interacted with the ocean, it would intensify.

"As the low deepens, it will form into a closed low pressure system," Ms Kirkup said.

"Where this low moves will determine where the more significant rainfall occurs."

The latest prediction is that the rain will fall heaviest in the Illawarra and the South Coast regions, with strong winds and large swells offshore.

"In these areas, we may see between 80 to 100mm of rain in several places," she said.

She said anyone travelling into these areas should stay in touch with developments in the weather in case conditions deteriorate further.

She urged anyone planning to holiday down on the coast next week to check the forecast on Sunday.

"We could expect some very strong winds along the coast and that is expected to whip up the sea so we may see dangerous surf conditions develop as we go into Monday," she said

"People holidaying by the coast may be impacted. It's a just a case of knowing whether it's your location or not."

Severe weather forecaster Dennis Luke, who provides information on impending storms and other severe weather for agencies like Victoria's Country Fire Authority, said he expected parts of the ACT could receive up to 60mm on Sunday night and into Monday.

"It will pass through reasonably quickly but there's potentially a good volume of rain to come," he said.

"Anyone down on the coast can expect very windy conditions and a swell of around 15 feet [five metres] hitting places like Merimbula."