Three people struck by lightning during wild Perth storm

Three people are lucky to be alive after being struck by lightning during a severe thunderstorm in Perth on Monday morning.

In Hammond Park a brother and sister were struck while sheltering from the storm under a tree.

Gerald Soh was driving past when he saw the pair suddenly jolted backwards.

"They were standing under a tree holding an umbrella and the next moment they were thrown backwards about one metre," Mr Soh told 9NEWS.

Both were taken to hospital with non life-threatening injuries and have since been discharged.

In Parmelia a man was working on his computer when he felt a shock from a lightning strike next to his house.

The bolt hit his neighbour's tree, ripping off bark, cutting a two-metre line through turf in his front yard and damaging articulation.

"Maybe we both go the same (lightning) fork and it split, one went this way and one went his way," neighbour Tom Wilson said.

"It was loud, it was like maybe a jet plane sort of landing on your roof."

The electrical storm lasted six hours and the lighting struck from Ocean Reef to south of Rockingham, closing many popular Perth beaches.

At the height of the storm 10,000 properties were without power.