UPDATE: HUGE seas and strong winds are lashing southeast Queensland's coast as some parts brace for flash flooding.A huge trough that crossed over the coast about 12.30am this morning is expected to dump up to 200mm of rain on central and southeast Queensland into the early hours of tomorrow.
Heavy erosion from big swells has closed beaches on the Gold Coast and the Sunshine Coast.
Surfers Paradise Beach is expected to take another battering after becoming a dangerous three-metre cliff following ex-tropical cyclone Oswald in January, with stairs and walkways to the sand being ripped out of the dunes.
Sunshine Coast lifesaver Rhys Drury says huge swells from strong east-northeasterly winds are set to worsen.
"It's a pretty horrible day down here on the beach," he told ABC radio on Monday.
"The winds are quite strong ... and they'll get stronger as the day goes on."
Weather bureau senior forecaster Vinord Anand says rainfall is likely to be heavier on the coast.
"If it was spread out over a day or two it would be alright but if it falls in the next six to 12 hours that can cause big problems," he said.
The State Emergency Service has responded to 40 calls for help on the Gold Coast and recently flood-devastated Bundaberg, mainly for leaking roofs, a Department of Community Safety spokeswoman told AAP.
The rain is expected to get heavier over the next 24 hours and could cause flash flooding in Gladstone, Gympie, Bundaberg, Kingaroy, Hervey Bay and Fraser Island, the Bureau of Meterology says.
Residents are also on alert for possible flooding on the Sunshine Coast, along with Brisbane, Ipswich and the Gold Coast.
Some areas are likely to see 100 to 200 millimetres of rainfall until the early hours of Tuesday morning, the weather bureau said.
Other areas could see over 100mm in just six hours.
It will be heaviest rain for many parts of southeast Queensland since ex-tropical cyclone Oswald raged during the Australia Day long weekend.