South-east Queensland has been smashed by overnight rains and flooding described as the heaviest downpour in more than a decade.

Major highways have been inundated, theme parks have closed and dozens of motorists have been stranded as up to 300mm of torrential rain pelted Australia’s east coast.

The downpour comes after months of drought and fire hazards, bringing relief to affected parts of Queensland and northern NSW.

Gold Coast was hit hardest, with 325mm of rain falling at Loders Creek and more than 200mm in the Gold Coast Hinterland.

Two people were rescued after trying to drive through floodwater on the Gold Coast, with police receiving more than 50 reports of flooded roads across the city on Saturday morning.

About half of Queensland was declared in drought, including Brisbane, the Gold and Sunshine Coasts, Redland and Moreton Bay council areas.

Most of the NSW coast and central and inland regions were also deemed “extreme drought”.

According to the weather bureau, triple the monthly rainfall has fallen on the Gold Coast in the past 12 hours.

100+ mm of rain for many locations across #SEQld overnight/early this morning. Heavy, intense rainfall has eased, but showers and thunderstorms still possible through the weekend. Take care on the roads – if it’s flooded, forget it.
Rainfall observations: https://t.co/aiVXf9eg8r pic.twitter.com/0BoIkXuALU

— Bureau of Meteorology, Queensland (@BOM_Qld) January 18, 2020

The State Emergency Service (SES) has been called to more than 150 jobs across the region over the same period.

At 12pm, the M1 remained closed at Helensvale as emergency crews try to pump floodwater away. Heavy trucks are being allowed to pass through, but cars continue to be diverted.

The wet weather is expected to continue for Queensland and NSW, with cooler temperatures and humid air easing conditions across fire grounds along the NSW south coast, albeit with less rain cover.

Theme parks Warner Bros Movie World, Dreamworld and Whitewater World Theme Park have closed to the public.

“Please be aware that due to severe weather and flooding, Warner Bros. Movie World will be closed today for the safety of our guests and team members,” Village Roadshow said in a social media post.

The Australian Reptile Park on the Central Coast was forced to close for the day as a result of the huge deluge.

The Australian Reptile Park was forced to close its gates for the day, Friday, January 17, after a downpour, the likes of which the country hasn’t seen in months, caused a flash flood.

(Reuters) pic.twitter.com/dGHrJqiyxI

— The Voice of America (@VOANews) January 17, 2020

Relief for NSW

The heavy rainfall will continue to provide relief to parts of drought-stricken NSW on Saturday after a long period of hot, dry weather and high bushfire risk.

Towns like Bundarra experienced 105mm in a 24-hour period as farmers raced outdoors to celebrate and feel rain on their faces.

“(The NSW south coast) won’t see huge rainfall totals but it does mean the fire danger will be decreased,” BOM NSW meteorologist Katarina Kovacvic told The New Daily.

Battered regions such as Bega, Batemans Bay, Eurimbula and Eden are set for temperatures in the low 20s but rainfall will be much lower at about 5mm.

The slow-moving cell is now impacting northern NSW as the storm cell moves offshore, but more rain has been forecast for the region across the weekend.

The thunderstorms and heavy rain are expected to continue all the way down the NSW east coast but lessen towards central and southern regions of the state.

“There is an 80 per cent chance of more storms and shower activity, but nothing to the extent that we have seen overnight,” a BoM spokesman said.

Sydney is expecting more rainfall of up to 50mm after Friday’s falls and further showers on Sunday.

Victoria battling smoke and fire

Conditions haven’t improved in Victoria, as bushfires continue to displace residents, with an evacuation notice for some northeastern communities in place overnight.

There were more than a dozen blazes still raging in Victoria on Saturday morning, predominantly in East Gippsland and the northeastern alpine region.

Most were burning at “watch-and-act” level or lower, but emergency warnings were issued for fires near Mount Buffalo in Victoria’s alpine region, and briefly for Bulart, in the state’s southwest.

Smoke is also expected to return to central Melbourne on Saturday and Sunday as easterly winds cross firegrounds.

Emergency Management Victoria has forecast the air quality will range from good to poor across the state, with areas closest to the fires experiencing the worst haze.

Incident management specialists from the US and Canada are set to arrive at Melbourne Airport on Saturday morning, ahead of being deployed to fires in the northeast and East Gippsland.

-with AAP