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Multiple states are set for a wet and stormy end to Christmas Day, forecasters have warned.
Sydney and other parts of NSW are in line for "very severe" thunderstorms this evening with the SES warning the city as well as the Northern Rivers could be badly hit.
The services said hundreds of volunteers are already on standby after almost 500 calls for help were made during a storm last night, over 300 of those in the city.
SES Deputy Commissioner Debbie Platz urged residents to stay inside saying even though it might be sunny for Christmas Day afternoon, bad weather is on the way.
READ MORE: Christmas day weather guide: Capital city state-by-state forecast
Anybody travelling for the festivities should take extra care, she said.
A total of 25 people had to be rescued from floods in Sydney last night.
"If you have to drive on the roads please stay out of flooded waters, please plan your route carefully, not just your destination but the route you are going to get there and pay heed to all the water warnings," she said.
The severe thunderstorm warning was extended to those in the Central and Southern Tablelands, North West Slopes and Plains, South West Slopes, Snowy Mountains, the ACT, Hunter, Illawarra, South Coast, Northern Tablelands, Mid North Coast, Central West Slopes and Plains and Riverina Forecast Districts.
The Bureau of Meteorology is warning Boxing Day could be another stormy day across eastern New South Wales and the ACT.
Flights were hit Sydney Airport on Christmas Eve, with images showing a deluge of water on the tarmac and even leaking into the domestic terminal.
Heavy rainfall, "large-to-giant hail", and damaging-to-destructive winds are forecast for Christmas Day and Boxing Day in multiple areas, including Canberra, Sydney, Brisbane and Melbourne.
Thousands of residents on Australia's east coast were left without power overnight after the storms, including in parts of Brisbane.
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New South Wales
Emergency crews responded to almost hundreds of calls for help on Christmas Eve, including 25 flood rescues.
The majority of the rescues were for vehicles trapped in flood water and following heavy rainfall in Sydney and Illawarra .
NSW SES Acting Assistant Commissioner Allison Flaxman urged residents to stay safe with more rain on the way.
"There is a possibility isolated heavy rainfall totals will exceed 200mm in some parts, which will bring a risk of flash flooding," she said.
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"NSW SES has prepositioned assets and has flood rescue teams prepared to respond should they be required."
There were also several reports of homes impacted by the flash flooding, with water leaking through roofs and under doors into garages and car parks.
"Fortunately there were no reports of significant injuries or major damage from the flood rescues," Flaxman said.
READ MORE: Storms head to most states for Christmas
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Flights were affected at Sydney Airport and thousands in Brisbane told they might not get power back until Christmas Day.
Victoria
More storms including hail is on the way for Victoria including Melbourne, East Gippsland, North East and Northern Country Forecast Districts.
About 20,000 people across regional Victoria lost power on Christmas Eve after storms lashed the state, Powercor confirmed.
The outage continues to affect about 6,100 residents across the state after new storms created more faults in the network.
Severe thunderstorm warnings are in place for parts of the state's north, including Central, East Gippsland, North Central, North East, West and South Gippsland and Northern Country Forecast Districts.
A flash flood Watch and Act warning has been reduced to an Advice level for St Arnaud in the Northern Grampians almost 250km from Melbourne.
Queensland
The south-east of the state is cleaning up after severe weather brought hail, creating a "white" Christmas of hail.
Thousands of homes were plunged into darkness on Christmas Eve as fallen trees caused havoc to the energy grid.
Power has been restored to about 57,000 residents, Energex confirmed.
Severe with damaging winds, heavy falls and large hail is forecast for Brisbane, the Gold Coast and the Sunshine Coast with conditions easing on Boxing Day to light showers and a possible storm.
A severe thunderstorm is on its way to residents in parts of Central West, Maranoa and Warrego and Darling Downs and Granite Belt Forecast Districts.
Dozens of roads were out of action in Brisbane and on the Gold Coast.
The small community of Gatton, west of Toowoomba, copped the worst of it.
Hail stones were more than 10 centimetres in size and smashed Dianne Castledine's solar panels.
"We were all settling in for and looking forward to Christmas Eve and the next minute it was just like bombs were dropping on the roof," Castledine told 9News.
"I have never seen hail like this before, never ever in all my years of driving I have never had hail damage to my car."
The Wivenhoe Dam west of Brisbane received 58 millimetres in just 30 minutes and the area saw more than 200,000 lightning strikes.
