The weather bureau expected tidal peaks to exceed the highest tide of the year by a metre at exposed beaches because of the big swell generated by Cyclone Oma, combined with king tides.

Excavators and boulder-laden trucks had been called in at the Gold Coast to build a seawall to protect the coastline, with the threat of erosion to increase on Thursday as conditions worsened.

At 10am on Thursday, Cyclone Oma was 890 kilometres north-east of Brisbane in the Coral Sea. Since 5am Wednesday, it had moved 230 kilometres towards the mainland.

The Bureau of Meteorology issued the first cyclone warning just after 11am on Thursday for areas between Bundaberg on the central coast and Ballina in NSW, including Brisbane, Sunshine Coast and Gold Coast.

"Tropical Cyclone Oma is expected to continue moving in a general south-westerly direction towards the south-east Queensland coast during today and Friday, whilst maintaining category 2 intensity," the warning read.

"Oma's motion becomes slow moving during Saturday but is then expected to track in a more north or north-west direction, remaining offshore through the weekend.

"Although Oma is not expected to make landfall in the coming days it will be close enough to produce direct impacts along the Queensland and New South Wales coast."

Tropical Cyclone Oma is the first cyclone in almost three decades threatening to strike Brisbane but meteorologists expect it to turn away at the last minute.

The last cyclone to reach Brisbane was Cyclone Nancy in 1990, which grazed the Byron Bay coast and resulted in coastal erosion and flooding.

Meteorologist Kimba Wong said the category 2 system was expected to move south-west at 11km/h in coming days and approach the coast this weekend.

"It is less likely a coastal crossing will occur," she said.

"There are a lot of variations from Saturday, it [Cyclone Oma] could linger off the southern Queensland coast, head north-west or heading to the south-east."

Ms Wong said the latest forecasts indicated the heaviest rainfall would be concentrated on the Sunshine Coast and Fraser Coast.

"We're expecting totals of up to 100 millimetres per day over the weekend in the Sunshine Coast and up to 50 millimetres per day in Brisbane," she said.

"Of course, there is the possibility of isolated heavier falls in excess of 300 millimetres near system's centre, depending on where it goes."

Ms Wong said the weather bureau expected damaging winds to arrive on Friday with average speeds of 90km/h.

Category 2 systems can produce gusts of up to 164km/h and the gusty conditions were expected to continue during the weekend.

Premier Annastacia Palaszczuk said natural disasters "just keep coming", following catastrophic fires and floods.

"I think we have had unprecedented weather events in Queensland over the last two to three months, unprecedented on the scale of which I've never seen before," she said.

Ms Palaszczuk said preparations had begun with relevant mayors and it was likely there would be a Queensland Disaster Management Committee meeting on Friday morning.

"The problem at the moment is that although it's sitting off the Queensland coast, the Bureau of Meteorology cannot put a direct path that it will take," she said.

"It's a cyclone, they are unpredictable and we do know that there could be waves between five and seven metres, I'm being told."

A flood watch has been issued for coastal catchments and inland areas between Gladstone and the NSW border, with major flooding possible during the weekend and early next week.

Police warned swimmers and boaties to stay out of the surf, with Cyclone Oma expected to whip up towering waves and ferocious winds.

Water police Sergeant Jay Bairstow said predicted eight-metre waves and 110km/h winds were deadly hazards for beachgoers.

Cyclone Oma weakened to a category 2 storm on Wednesday and combined with a king tide and the powerful swell low-lying streets on the Gold Coast and Brisbane were flooded.