THERE is a moderate risk of a cyclone forming late on Tuesday.
A weak tropical low has formed more than 100km north of the Arnhem coast in the Arafura Sea.
The low is expected to move west or southwest towards the Timor Sea and slowly deepen.
A cyclone could affect the Kimberley coast by this Wednesday.
Weather Bureau senior forecaster Rebecca Patrick said that the path of the low-pressure system was unpredictable.
"It may well move over land or water," Ms Patrick told the Sunday Territorian.
"There will still be a lot of rain," she said.
There is a low chance of a cyclone occurring today and tomorrow.
Ms Patrick said there will certainly be strong north-westerly winds if the trough moves to the west.
That will please Darwin surfers.
The low is in a weak monsoon trough over the Arafura Sea and is threatening to become more active as it moves closer to the Top End coast.
The Weather Bureau is warning of flooding today in the Top End.
Thunderstorms and isolated showers of up to 80mm may lead to localised flooding and higher water levels in creeks.
Darwin was hit by a few millimetres of rain yesterday, while Alice Springs is getting sunny conditions with temperatures in the mid-30s.
Adelaide River had the most rainfall in the 24 hours to the time of writing, with 51mm of rain.