The day fire, thunder, hail hit Gingin

Damage done: Marek Kwiecien-Fisher inspects his battered blueberry crop. Picture: Ian Munro/The West Australian

Residents near Gingin are counting the cost of violent weather that tore through the region on Wednesday and caused them to fear for their lives.

Bushfire, torrential rain, tornado-like winds, deafening thunder and gleaming lightning hit dozens of properties north of Perth in a few hours on Wednesday afternoon.

At Regan's Ford, 140km north of Perth, backpackers Mami Nakada, Manaka Murakami and Kevin, who did not want his last name used, huddled together in the back room of a house at an olive farm as a mini-tornado ripped off the roof.

"We thought we were going to die - it was the scariest experience of my life," Ms Nakada said.

"Our boss had told us there was a bushfire coming so we were watching out for that. Then we saw heavy rain and the wind was crazy.

"We hard a big bang and we thought it was thunder, but it must have been the roof coming off. We stayed together and tried to protect our heads."

Regans Ridge Olives owner Catherine Lee returned to find the devastation. "It was just awful - we had fire, rain, hail and a tornado in the space of three hours," she said.

"We are happy the oil has been saved, so we haven't lost any product, just an olive processing shed, a machine and the roof."

Next door, farmer Marek Kwiecien-Fisher lost the roof off a house and close to $1 million of blueberries and olives.

Despite frantic efforts to save his blueberry crop, Mr Kwiecien-Fisher lost about $300,000 of the fruit. Hail pounded his olive trees, causing an estimated $500,000 damage.

About 20km away in Wanerie, a 5km firefront razed more than 8000ha and flattened one house.

Cecil Campbell, who lives next door to the destroyed property, worked tirelessly to save his own home and helped his neighbour fight the blaze.

"I've never seen lightning like it. It would strike and you'd see a fire start," he said.

It took 250 firefighters about 30 hours to contain two major blazes in Wanerie and Red Gully.