Sky like 'atomic bomb cloud' near bushfire

Residents who fled a bushfire south of Perth have described the ferocity of the blaze as "horrific" and like an "atomic bomb" cloud.

Smoke clouds caused by a large bush fire near the town of Waroona and the surrounding area seen from the turn off to the South Western Highway near Pinjarra, Western Australia. Source: AAP

A man who lost his business in a bushfire burning south of Perth says the sky looks like an "atomic bomb has gone off".

The Department of Fire and Emergency Services has warned lives and homes are in danger in Waroona, Harvey and surrounding areas, including Preston Beach, and urged many to pack up and leave.

Drakesbrook Fine Wine owner Bernie Worthington lost his hillside vineyard, olive grove and orchard in Waroona - destroyed in the early hours of Thursday morning after his family escaped their under-threat home.

"It looks like a mushroom ash cloud in the sky, like an atomic bomb has gone off," he told AAP.

"We found out from a neighbour at daylight that it's all gone.

"It's the end of the line now. We haven't got the money or energy to start the business again."

Authorities have told Mr Worthington it will be days before his family can return to the property.

Waroona Hotel owner David Burt described billowing clouds of thick smoke with sudden flare-ups that have darkened the skies above the town.

"I get the feeling people are more worried about this fire than the one last January," he told AAP.

"When you know that all the efforts are going to danger spots to save lives and houses, you know that there are other areas unchecked.

"I've got my car packed and pointed in the right direction ready to leave. If it gets dangerous, we won't stay and fight."

The family-run hotel has been supplying meals to neighbours using a generator after the power in the area was lost.

Melissa Young lives on a 90-hectare property about 12km out of Waroona and was forced to evacuate on Wednesday night.

"I was sitting in my lounge when I heard a clap of thunder," she said.

"I looked out the back there and my goodness it was a massive fire."

Ms Young grabbed her dog and evacuated.

"I watched this amazing, ferocious thing. The speed was insane, it engulfed everything," she said.

The bushfire, sparked by lightning, was reported just before 7.30am on Wednesday and has burnt more than 21,000 hectares.