The weather bureau says there is a high chance of a cyclone developing off the Northern Territory coast early this week.
The tropical low is developing over the Arafura Sea, about 500 kilometres east-northeast of Darwin, moving in a westerly direction.
Angeline Prasad from the Bureau of Meteorology says if enough of the low stays over water, it could develop into a tropical cyclone.
"For Monday we are going for a moderate chance of it becoming a tropical cyclone, and on Tuesday we have upgraded it to a high chance of becoming a tropical cyclone," she said.
"So for Monday its a 20 to 50 per cent chance, on Tuesday its about a 50 per cent chance."
The closely for the risk of gales developing over the western coast and northern Western Australia during Tuesday and Wednesday.
© ABC 2014
11:20 EST Since the the royals stepped off the plane on Wednesday afternoon, Sydney has turned on the great weather.