Two volunteer firefighters have been burned battling an out-of-control bushfire spreading in multiple directions.

Paramedics treated the firefighters at a blaze north of Perth on Wednesday.

A man in his 60s was airlifted to Fiona Stanley Hospital with non-life-threatening.

The other firefighter sustained minor injuries.

They were among dozens of crews battling a fire in coastal scrubland that was upgraded to emergency level on Wednesday.

An emergency warning is in place for parts of Wedge Island, Nambung and Cooljarloo in the Shire of Dandaragan.

It includes the coastal fishing villages of Wedge and Grey.

"If the way is clear, leave now for a safer place," the Department of Fire and Emergency Services said in an alert on Wednesday.

Parts of Indian Ocean Drive and surrounding roads have been closed and residents have been told to leave in a northerly direction towards the town of Jurien, about 220 kilometres north of Perth.

"The bushfire is moving in multiple directions due to variable winds," the emergency warning said.

"It is not contained or controlled."

The nearby Cervantes townsite is under a watch and act alert.

The fire was reported on Monday, escalating to emergency level on Tuesday before being downgraded.

The top-level warning was re-issued Wednesday due to the changing fire conditions and about 60 firefighters with ariel support are at the scene.

The blaze has burned through about 37000 hectares of bushland, with no reports of property damage.

An evacuation centre is open at Jurien Bay Sports and Recreation Centre.

Cervantes Primary School is and will remain closed on Thursday.

Nambung National Park has also been closed.

By Aaron Bunch in Perth