She's not done yet. Cyclone Debbie has saved a special serve for Sydney and northern NSW, with the remnants of the cyclone which devastated Far North Queensland set to give us a soaking on Thursday and Friday.

Debbie has been downgraded to a tropical low, but the wild weather is still walloping Queensland and is sneaking interstate, with northern NSW residents preparing for torrential rain, flash flooding and wild winds as Debbie's leftovers head south, according to news.com.au.

Her march will run smack-bang into a cold front moving through NSW on Thursday, and the result is up to 200mm of rain and gale force winds are expected in some areas, stretching from South East Queensland down the NSW coast from Tweed Heads to Sydney, according to the Bureau of Meteorology.

The Northern Rivers will cop the worst of the NSW weather, with areas from Tweed Heads to Taree to be wettest. Flooding is predicted, along with damaging winds.

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Sydneysiders can expect another dose of the humidity which has gripped the city in recent weeks, and heavy rain on Thursday.

Sydney has no flood warnings in place, but will be decidedly soggy, with heavy showers at times, and a predicted 20mm-plus of rain and fierce winds.

The BoM has a severe weather warning in place for the Northern Rivers, Mid North Coast, Hunter, Sydney and surrounds and the Northern Tablelands warning of heavy rain over through Thursday and Friday.

It also warns of damaging winds averaging 65km/h and gusts or up to 90km/h along the coast from north of Sydney to the Queensland border.

Meanwhile, Queensland is counting the cost as the extent of Cyclone Debbie's devastation emerges.

Authorities are today trying to get food and drinking water to people in Far North Queensland left without essentials - or access to them - by the storm.

Power remains off in many areas, and dangerous weather conditions and torrential rain are hampering access efforts.

Since dawn broke images of shattered homes, businesses and critical infrastructure have steadily emerged, and it's now certain the state faces a long and very expensive road to recovery.

Later this week the low pressure system will be over the populated southeast corner, and could cause flash flooding into Friday before it moves offshore, the Bureau of Meteorology has warned.

Queensland Premier Premier Annastacia Palaszczuk has warned some people could be without power for up to a week. On Wednesday morning, 63,000 households were going without.