NASA captures image of Northcliffe blaze from space

The Northcliffe fire threatening homes and lives in Western Australia's south is big enough to be seen from space.

NASA has captured a satellite image showing the extent of smoke cover smothering the state's southwest corner, drifting out over the ocean.

However, the picture was taken earlier this week - and overnight, the blaze has doubled in size.

The fire, which is heading straight for the townships of Northcliffe and Windy Harbour, burned through more than 22,000 hectares last night, bringing the destruction to a total of 48,000 hectares.

Residents in Northcliffe and the subdivisions of Parkview, Bracken Rise and Double Bridge have been told their town sites are "undefendable" and they must leave.

The town of Pemberton, which was originally the evacuation point for Northcliffe residents, is also on alert.

Residents have been told they will need to leave if the fire overruns Northcliffe.

Authorities say it is not safe to leave Windy Harbour and have advised people to seek shelter at the beach.

A Department of Fire and Emergency spokesman said people at Windy Harbour might have to be leave by boat or helicopter.

About 200 firefighters and 60 support personnel are battling the blaze, which has a 196km perimeter.

More than 100 Victorian firefighters will be integrated into existing crews and will begin shifts battling the blaze tomorrow.

Spot fires are starting up to 100 metres ahead of the fire and winds are expected to be gusty throughout the day.

One house and a shed have been destroyed.

With AAP.