Temperatures will remain between 24 and 26 degrees between December 11 and 14 but heavy showers will dominate the weekend with the heaviest falls, up to 50-60mm, expected on Friday and again on Monday.

The State Emergency Service (SES) said storms are also possible along the coast and are advising residents to ensure properties are storm-ready.

The BoM says a high pressure system over the Bight is extending a ridge across New South Wales but will weaken by Thursday allowing a trough to move through southern and western parts of the state.

At the same time, a new high pressure system is forecast to strengthen south of the Bight then drift slowly east through the weekend.

"This system looks set to be the dominant feature in the region for a number of days, and has potential to bring significant rain to parts of the coast, particularly in the north," a BoM spokesperson said.

The Bureau has issued its outlook for summer as Australia continues to experience an active La Nina event which is expected to remain until at least the start of autumn.

The Bureau's Head of Operational Climate Services Dr Andrew Watkins said this means large parts of eastern Australia have an increased risk of flooding.

"Our climate outlook is the opposite of what we experienced last year in Australia. This summer, New South Wales, Victoria and Queensland are expected to see above average rainfall, meaning we face an increased risk of widespread floods.

Dr Watkins said that while the risk of bushfires isn't as high as last summer, fires will occur.

"There's a great chance of grass fires in some areas as recent rain and warm weather have led to vigorous vegetation growth. South eastern Australia is one of the most fire-prone regions in the world. Even short periods of hot and dry weather increase the risk of fire in summer."

Dr Watkins said the outlook was also a reminder for communities to be prepared for heatwaves over the coming months.

"Every summer we see heatwaves across southern Australia. This summer heatwaves may not reach the extreme temperatures of recent years, but may be longer duration and more humid, which can still have a significant impact on human health."

Dr Watkins said northern Australia remains on track for an average to slightly above average cyclone season.

"On average, Australia sees 9 to 11 tropical cyclones each year, with 4 crossing the coast. The first cyclone to develop in the Australian region occurs earlier during La Nina years.

"People in the north of the country should prepare for tropical cyclones now. And don't forget tropical lows, which can bring heavy rainfall, flooding and cause significant property damage."

Thank you for valuing local journalism with your subscription. While you're with us, you can also receive updates straight to your inbox from the Port Macquarie News. To make sure you're up to date with all the news, sign up here.