Cyclone Kelvin has been upgraded to a category two system as it crosses the northern coast of Western Australia, with the storm bringing even more rain to the drenched region.

A red alert has been issued for people from Bidyadanga to Sandfire including Bidyadanga in the Pilbara and Kimberley regions with the cyclone making landfall near Anna Plains Station, south of Broome.

The Department of Fire and Emergency Services (DFES) said there was a threat to lives and homes, and people were in danger and needed to act immediately.

A yellow alert remains in place for people between Broome and Pardoo Roadhouse but not including Broome.

The Bureau of Meteorology (BOM) upgraded the cyclone to a category two as it approached the coast between Sandfire and Bidyadanga, bringing destructive winds of up to 150 kilometres per hour near the centre of the system.

A live wind map showing Cyclone Kelvin hovering over WA's far north

Gales with gusts of up to 100kph are possible in remaining areas between Bidyadanga to Wallal Downs.

Heavy rainfall is likely to continue over the west Kimberley and far east Pilbara throughout the day.

The system, which was upgraded from a tropical low to a cyclone yesterday afternoon, was initially forecast to develop into a category three but weakened while tracking towards the west Kimberley coast.

Andrew Burton, senior forecaster at the Bureau of Meteorology's tropical cyclone centre, said the Kimberley and Pilbara could expect a drenching.

"I think we've already seen one of the strongest impacts of this system that Tropical Cyclone Kelvin will have — [that] is the rainfall we've seen in Broome," he said.

"We've had 370.6 millimetres up to 9:00am [Saturday] and that rainfall is continuing, so they look like they're on track to get to their wettest year ever."

Broome has recorded almost 90mm in additional rainfall in the 24 hours to this morning.

Fears flooding could damage roads

The deluge of rain has forced the closure of parts of the Great Northern Highway, and localised flooding is expected at floodways across the East Pilbara and the West Kimberley.

Main Roads regional manager Andrew Pyke said the heavy rains could end up closing major arterial roads and highways, with the area already having major rainfall.

He said crews were closely monitoring the situation but there were fears conditions could deteriorate.

"From a flooding perspective, it's a bit of a perfect storm," he said.

"We've got a lot of water sitting on the Roebuck plains area now and a lot of water happened in the last 24-48 hours in the Broome area, and there is more water coming down with the passing of this cyclone.

"It is quite difficult. There's certainly been significant damages of some roads in the Kimberley with the water that's flowed over the roads. We are very concerned."

The WA Water Corporation has also warned residents not to swim, fish or play in Roebuck Bay or Dampier Creek in Broome after the heavy rains causing wastewater to overflow.

The Broome South Wastewater Treatment Plant began to overflow treated wastewater.

The wastewater which overflowed is not raw wastewater, and the Water Corporation said the majority of the overflow was stormwater.