Residents across south-east Queensland are being urged to prepare for more flooding as heavy rain continues to lash the region.

A man drowned yesterday afternoon trying to cross a flooded road at Kilcoy, north of Brisbane.

The body of the 77-year-old Sunshine Coast man was found by police after his car sank in floodwaters.

Further north, a woman remains missing in bushland after fleeing rising waters at Pomona, in the Sunshine Coast hinterland.

Yesterday, a family of three escaped unharmed after their car was inundated in the town.

South-east Queensland is on flood alert as the weather bureau predicts up to 200 millimetres of rain will fall in the next 24 hours.

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While the rain is nowhere near as heavy as that recorded during the Australia Day long weekend when ex-cyclone Oswald caused widespread flooding, authorities are still warning that flash flooding is possible from Bundaberg south to Brisbane.

Overnight, residents in low-lying areas of the Lockyer Valley, west of Brisbane, were urged to evacuate as Laidley Creek continued to rise.

With flooding expected in the area by early morning, evacuations centres have been set up at Laidley State High School and at Alexandra Hall in Toogoolawah.

In Gympie, businesses in the CBD will be flooded for the second time this year, with the Mary River expected to peak at 16 metres by 9am AEST.

Mayor Ron Dyne says the Kidd Bridge was cut overnight and the Normanby Bridge was expected to be flooded.

Councillor Dyne says at this stage, homes are unlikely to be affected.

"We are expecting a high of 13 metres at 11 o'clock to 12 o'clock tonight and about 16 metres by nine o'clock tomorrow morning," he said.

"Now 16 metres indicates that some businesses in the CBD will be impacted by water because they'll go in at 15.1 metres."

Emergency services are urgently calling on motorists to avoid non-essential travel and not to cross flooded roads in the state's south-east.