The chance of a cyclone forming in the Top End of the Northern Territory on Friday is now considered a 50 to 100pc possibility, according to weather forecasters.

A monsoon trough off the north coast is expected to develop into a tropical low today.

Quoted by Weatherzone, Bureau of Meteorology forecaster Angeline Prasad said the system has already caused heavy rains of up to 100 millimetres in some parts of the Territory.

"We are expecting the system to form in the Arafura Sea in the next 12 to 24 hours," she said yesterday afternoon.

"Once the low pressure system forms, it is expected to remain slow moving over the next few days and gradually intensify.

"We have got a moderate chance of development on Thursday and a high chance of it becoming a tropical cyclone on Friday."

The Weather Channel has reported that the potential also exists for a second tropical cyclone to form over Australian waters later in the week, as the monsoon trough becomes established for the first time this wet season.

In addition to the tropical low that has already formed in the Coral Sea, the Weather Channel said a second tropical low should gradually form near the Top End coast with the potential to deepen into a tropical cyclone later in the week.

“This system will form close to the coast and will help cause heavy monsoon rain and flooding over the Top End this week with over 200mm of rain possible along the north coast of the NT,” Weather Channel senior forecaster Tom Saunder said.

“Computer models which forecast the movement and intensity of weather systems are currently in disagreement regarding the location or timing of a coastal impact.”

The Northern Territory Emergency Service says people should start preparing in case a Cyclone Watch is declared later this week.

Emergency Services director Peter Davies said Top End residents should be thinking about where they will shelter and should also consider insurance.

"If you have not cleaned up your backyard, if a Cyclone Watch is declared you are going to find that there are going to be long queues at the tip," he said.

"And also, quite importantly, if you haven't got your insurance and you are thinking about doing so, well, once the Cyclone Watch is declared, most insurance companies won't insure you for that period."

Meanwhile, Victoria's Wimmera region is recovering from last weekend’s heavy rain and flash flooding, where up to 100 millimetres of rain over the weekend caused sheep losses and infrastructure damage to several properties.