The weather bureau says it is highly likely a cyclone will form in the Coral Sea off north Queensland.
The low pressure system is currently situated 800 kilometres north-east of Mackay and is slowly moving east.
Bureau spokesman Chris Joseph says it should continue on that path until the weekend but it is difficult to predict what it will do after that.
"There is a high degree of uncertainty as to what will happen with the system after the weekend," he said.
"The modelling does suggest that it could take a more southerly path but it all depends on the other systems at play that would influence its movements."
Senior forecaster David Grant says it is too early to tell where it will go if it becomes a cyclone.
"At the moment it is in a developing phase ... and it is rated as a high chance of developing into a tropical cyclone from today onwards," he said.
"Whether it doesn't impact on the coast in the longer term, most people should be prepared now where it does impact on the coast in the next week or so."
© ABC 2013
17:21 EDT After a good soaking, there is more rain ahead for Western Australia's Pilbara and Gascoyne.