A very active cyclone season is stepping up around the Australian tropics, with the Bureau of Meteorology monitoring four significant systems spiralling around the country's north.

BOM's radar includes severe Tropical Cyclone Marcus, Tropical Cyclone Nora off Australia's north west, and two tropical lows to the north east.

Cyclone Marcus, off Western Australia's north west, is by far the most extreme of the systems.

The tropical cyclone, which battered Darwin as a category two system over the weekend, developed into a category five system this week to become the strongest in Australian waters for more than a decade.

Marcus recorded maximum average wind speeds near its centre of 230 kilometres per hour and wind gusts of up to 325kph.

Wind speeds above this intensity have not been witnessed in Australian waters since Severe Tropical Cyclone Monica in 2006.

It was downgraded Friday morning to a category four and is set to further weaken before heading towards the WA coastline over the weekend.

Sorry, this video has expired Wild winds and rain hit Darwin with Cyclone Marcus

Cyclone Nora to cross coast

Forecaster Jonathan How said the bureau was also following the development of Tropical Cyclone Nora in the Gulf of Carpentaria.

All warnings for the Northern Territory were cancelled late on Friday, but a warning remains in place from Thursday Island to Cape Keerweer in Queensland on the western part of the peninsula coast.

Mr How said tropical cyclones in the Gulf were "known for being quite erratic" and there was still a bit of uncertainty about exactly where it would track.

He said it was expected to make landfall somewhere along the eastern or southern Queensland Gulf coast.

Widespread flooding in northern Queensland earlier this month isolated towns and farmland, and inundated more than 200 homes.

"We're certainly keeping a very close eye on how the rainfall pans out there, because we could see communities continue to be cut off," Mr How said

Wind map showing Tropical Cyclone Nora north of the Gulf of Carpentaria in northern Australia.

Eyes on another two

Looking out towards the Coral Sea, models are also showing a tropical low that is bringing a lot of rain from the Solomon Islands down to New Caledonia.

Mr How said there was a slim chance the system would became a tropical cyclone.

"We can't rule it out, but it looks like there will be generally unfavourable conditions for the system developing," Mr How said.

The system is expected to move towards the east and into Fiji's area of responsibility into next week.

The BOM said it was yet to put out any official advice for a developing tropical low even further to the north west in the Indian Ocean, which is also unlikely to form into a cyclone.

"We definitely can't rule it out … some of the models are suggesting that it will spin up into a cyclone, but other models aren't, and either way, it's not expected to have any impact on the continent," Mr How said.

Australia has experienced an active cyclone season so far, with seven systems entering its jurisdiction.