Flash flooding, beach erosion, abnormally high tides, huge swells, and damaging winds are just some of the extreme conditions residents of the Gold Coast can continue to expect for the rest of Monday, as a low pressure system and moist onshore airstream continues to lash Australia's unofficial holiday capital.

Brisbane and much of the Queensland coastline as far north as Bundaberg are also copping the brunt of the storm, while the NSW north coast - from the Tweed coast as far south as Kempsey - is also experiencing extreme conditions

Rainfall over the weekend was in the extreme range in many areas, with an incredible 738mm of rain in the gauge at Upper Springbrook in the 72 hours to 9am on Monday.

Image: Not the sort of weather Gold Coast holidaymakers were hoping for. Source: Pixabay.

For Gold Coast locals like "Tara", the wild weather meant a three-day weekend as she was unable to access her workplace in Surfers Paradise on Monday morning due to flooded roads and dangerous winds in the vicinity of her office.

"People were getting blown over walking between the buildings, so our office is closed," she told Weatherzone.

Tara said the low-lying parks near her home at Emerald Lakes, beside the Nerang River, were all inundated and the rain was "blowing sideways across the lakes".

But the most dramatic pictures in the last 24 hours have come from the coastline from the Gold Coast and Byron region, where severe erosion is turning beaches into cliffs of sand battered by a relentlessly raging surf.

Byron Bay main beach today ... and the rain just keeps falling. Not a good sign ahead of tomorrow’s king high tide of 1.91m https://t.co/VD4KU5w0Pa pic.twitter.com/njYHbwsrJR

— Scott Henry (@scoopnewsworthy) December 14, 2020

Warnings in place

Meanwhile Queensland Emergency Services Minister Mark Ryan warned residents to prepare for the worst, likening the ongoing storm to a tropical cyclone. "Many of the impacts from this weather event will be similar to a category-one cyclone event," he said.

Across the state, crews have been working to restore power to at least 16,000 homes, mainly on the Sunshine Coast. Queenslanders have been warned to stay off the roads, avoid unnecessary travel and never to drive through floodwaters.

All Gold Coast beaches are closed and a summary of Queensland warnings can be found here.

A severe weather warning for damaging winds, heavy rainfall, abnormally high tides, and damaging surf is also in place for a large slice of the NSW coastline from the Qld border down to just north of Taree.

So what's happening?

This is the first sign that the La Nina declared by the Bureau of Meteorology at the end of September is finally kicking in across this part of Australia's east coast.

Periods of sustained moist onshore winds are typical of weather patterns which become much more likely during a La Nina summer, and it appears that this particular weather system will stick around for a while yet.

Brisbane, the Gold Coast and the NSW north coast and mid north coasts can all expect further heavy rain through till tonight. The rain should ease off slightly in southeast Queensland in coming days, but heavy rain will continue to affect the NSW mid north coast on Tuesday.

In the cities, Brisbane can expect Monday's heavy rain to turn to showers on Tuesday, while Sydney – which so far has only received a light sprinkling from this system – can expect its heaviest rain of the week with between 10 and 20 mm of rainfall on the cards.

It should remain mostly wet in Sydney for the rest of the week, albeit without the heavy rain that has drenched areas further north.

Meanwhile the massive bushfire on Fraser Island is now under control, though not fully extinguished yet. The island has now been declared safe to visit again.