Authorities are keeping tabs on a low-pressure system off the Queensland coast which is threatening to put a dampener on the Easter long weekend.

The remnants of ex-tropical cyclone Iris are a few hundred kilometres northeast of Fraser Island, moving slowly southwesterly towards the coast.

Forecasters are expecting this will bring increasing showers along much of the Queensland coast from Saturday, becoming very heavy from Monday.

The weather bureau says it's a waiting game to see where the system crosses the coast, anywhere between the Capricornia region in central Queensland, north to the already rain-drenched parts of the state around Cairns and Townsville.

Depending on when and where the system hits the coast, it could bring falls of hundreds of millimetres and trouble for holidaymakers returning from the Easter break, state Disaster Co-ordinator Deputy Police Commissioner Bob Gee said.