Thunderstorms and rain are expected to continue across New South Wales and Queensland for the rest of tonight and into tomorrow.
The Bureau of Meteorology (BoM) said severe thunderstorms will carry on in south-east Queensland, between Harvey Bay and Mackay, through tonight.
Thunderstorms will also continue in north-east NSW throughout the evening and into tomorrow.
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A number of rescues have taken place in NSW today after heavy rainfall caused flash flooding in the Hunter region and north-east of the state.
A person became trapped inside their car after trying to cross floodwaters on Idaville Road in Merriwa in the Hunter region about 6.30am today.
He was found standing on the tray of his submerged ute as the river rose due to being inundated with rain.
Merriwa Rescue crews were joined by NSW Police and Ambulance to save the man, who was then taken to hospital.
His car was left in the floodwaters.
"It seems the individual has not appreciated the speed or the depth of the water that was flowing across the causeway and unfortunately half way along his vehicle has been swept off the causeway," Andrew Luke from Merriwa Rescue Squad said.
It sparked another warning for residents not to cross swollen rivers, or enter floodwaters.
"It's probably a stark reminder to others who decided it was a good idea to try it today," Mr Luke said.
Merriwa Rescue Squad said this was the second rescue this morning.
NSW Rural Fire Service (NSW RFS) also carried out a rescue in Forbes yesterday when a motorist was cut off by floodwaters.
She was driving down the Lachlan Valley Way when floodwaters cut off her access and she was unable to turn around.
The NSW RFS helicopter happened to be flying around the area and was able to land and safely relocate the woman.
"It's important to note that some roads maybe cut off with little warning."
"So even if there are no warning signs or road closed signs never drive through flood waters," NSW RFS said.
The NSW Hunter region has been particularly impacted by flooding today.
9News reporter Olivia Grace-Curran captured Dora the horse swimming through floodwaters in the Upper Hunter.
The horse's paddock has been turned into a pool after it became inundated.
Floods also impacted Tamworth in the NSW north-east amid heavy rainfall.
Some residents were unable to go into work as Calala Lane was filled with flood waters, cutting off their route.
The road has since reopened.
Some students sitting their HSC in Tamworth had to relocate.
Tamworth High School and Farrer Memorial Agricultural High School advised their HSC students to attend different schools to sit their exams, and advised all other students to remain at home or report to their closest public school.
Moderate flood warnings remain in place for the Castlereagh River at Mendooran and the Peel River in Tamworth.
The Central West which has already been battered by flooding has an upgraded major flood warning for the Lachlan River at Jemalong.
Multiple minor flood warnings have been issued for inland rivers in the north-west and central west.
A Hazardous Surf Warning has been issued for the Macquarie and Hunter Coasts.
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The Bureau of Meteorology (BoM) said another trough is expected to cross the state on Wednesday and Thursday this week, bringing more severe weather.
"Renewed flooding is possible in the inland rivers where there are minor to major flood warnings current," the BoM said.
The wild weather has already turned deadly, with a woman in her 30s has dying after being hit by a falling tree branch on the NSW Central Coast.
While two boys had to be rescued after being trapped in floodwaters in the NSW Lachlan River, with a police officer jumping in to save them.
Queensland
A severe thunderstorm warning remains in place for central Queensland, including Mackay.
The storm may bring heavy rainfall, damaging winds and large hail.
Further north, severe thunderstorms with heavy rain moved through south-east Queensland today.
This morning, Toowoomba was hit by severe storms, and Caboolture was lashed with torrential rain.
A total of 72mm of rain was recorded in Ma Ma Creek near the Lockyer Valley in just one hour and 23.6 mm fell in Brisbane between 6am and 9am.
The storm cell is expected to bring wet weather all week.
Queensland Fire and Emergency Services said there will be more severe storms and heavy rainfall this summer.
"There is a risk of increased weather activity in the coming months, so our communities need to be ready," Assistant Commissioner Gary McCormack said.
It comes as the BoM said there is a 66 per cent chance of a higher-than-average number of cyclones and rainfall for Australia's eastern region.
