Investigators are probing the crash, which claimed the lives of a 78-year-old woman and her 75-year-old male passenger.
Preliminary reports say the falling tree toppled onto the vehicle as it was driving along Graphite Road in Deanmill, a small town 300km southeast of Perth, on Wednesday afternoon.
Department of Fire and Emergency Services Superintendent Andy Wright said the pair had been on their way to Margaret River.
"The danger in some cases is that the tree is already down and across the road but, in this circumstance, it looks like the tree has hit squarely on the vehicle," he told reporters.
"(It was) a tragedy … our thoughts go out to the family."
A strong cold front swept through south-west — Bureau of Meteorology, Australia (@BOM_au) #WA yesterday and overnight, bringing showers, thunderstorms, and damaging wind gusts to some areas. Cold today with showers and small hail, easing into tomorrow. Latest: https://t.co/jlOoTZLz8d pic.twitter.com/kAQGO2QLnQAugust 1, 2024
Volunteer firefighters and SES workers helped clear the tree and remove the two people from the vehicle.
Both occupants died at the scene.
Crash investigators have called for witnesses to contact police.
Thousands of people across south-western Western Australia lost power on Wednesday evening as a severe thunderstorm driven by a strong cold front smashed the region with heavy rain and damaging winds.
Unseasonal rainfall is expected for parts of WA for the remainder of the week as the system moves north.
The Bureau of Meteorology has also issued a strong wind warning for the state's Leeuwin, Albany, Esperance and Eucla coasts.
8°C