Residents of Queensland’s Lockyer Valley have been urged to self-evacuate, with up to 160 millimetres of rain forecast to bring life-threatening flash flooding across the state’s south-east.

The Grantham flood siren sounded early on Friday to warn residents in low-lying areas to head to higher ground.

The Lockyer Valley Regional Council, about 100 kilometres west of Brisbane, urged residents not to wait for emergency services to evacuate them.

“The siren is intended to prevent any loss of life and relies on the community heeding the siren,” it said in tweet.

Tweet from @LockyerValleyRC

Lockyer Valley Mayor Tanya Milligan said modelling suggested up to 260 homes could be affected in areas including Laidley and Grantham. At least 100 millimetres of rain is forecast for Friday.

“The event that we had in February and March we had about 68 homes [inundated],” she told the ABC.

“It is soul destroying, it’s absolutely crushing.”

About 120 kilometres south-west, Stanthorpe residents are also on alert as Quart Pot Creek continues to rise.

The Southern Downs Regional Council said the creek was already at a moderate flood level on Friday morning, with more intense rainfall forecast.

“If the situation worsens, warn neighbours, secure property and prepare to move to higher ground,” it said in an alert.

More heavy rain is forecast across much of Queensland on Friday. Gympie, Bundaberg, Hervey Bay, Cooroy, Nambour and Rainbow Beach are also all on flood watch as a surface trough moves across the coast.

“Locally intense rainfall, which may lead to dangerous and life-threatening flash flooding, is possible with thunderstorms during Friday afternoon,” the BOM said in an alert on Thursday.

Senior forecaster Matthew Bass said the worst of the rain and storms would hit the south-east on Friday.

“Friday will be the worst of the rainfall for south-east Queensland but unfortunately it doesn’t mean that it will cease on Saturday, so we’re still likely to see that those onshore winds continue and that rainfall still pushing onto the coast,” he said.

Tweet from @BOM_Qld

Major flooding is forecast for Laidley Creek and the Mary River at Gympie.

QFES Assistant Commissioner Andrew Short said residents should resconsider their need to travel, with hundreds of roads already cut by floodwaters.

Almost 70 schools have already been closed.

“Currently, we’ve got 18 emergency alerts out in a number of councils,” he told ABC Radio on Friday.

“We’re looking for people just to listen and respond and act accordingly.”

Brisbane City Council has suspended ferry services and opened sandbagging stations, with residents in flood-prone areas being advised to move their cars to higher ground.

The lower Brisbane River is expected to reach a minor flood level on Friday morning, but Emergency Services Minister Mark Ryan said updated forecasts of intense rain could pose a risk of flash flooding into Saturday.

“Those falls could be up to 160 millimetres over six hours, so creek catchments could rise very quickly, particularly given the creek catchments are so water-saturated at the moment,” he told ABC Radio.

“Anyone who is in a creek catchment or river area needs to be very well aware of their circumstances because the rain can become heavy to intense very quickly, and that means that there is a severe risk of flash flooding.”

The Gold Coast has so far missed the most intense rainfall, but Mayor Tom Tate has opened sandbagging stations, warning of localised intense rainfall.

The continued rainfall comes as a man was found safe and well after disappearing near a campsite south of Gympie in the state’s south-east.

Police and swift water rescue crews had been searching for the 36-year-old after he was reported missing at 10am on Thursday.

He was last seen chasing his dog away from the Yabba Creek Road campground near Imbil about 11.30pm on Wednesday.

Floodwaters cut off access to the site with the RACQ LifeLight chopper deployed amid heavy rainfall.

Police confirmed the man had been located “safe and well” on Thursday afternoon.

A woman in her 30s died in floods near Mackay earlier this week as rains up to 10 times the monthly average battered the north and the central interior of the state.

A man in his 60s was also treated for hyperthermia after spending Wednesday night clinging to a tree after his car became swamped by floodwaters near Bundaberg.

This week’s heavy rainfall across Queensland is the state’s sixth major flood event since December with a combined death toll of 28.

-with AAP