A massive storm front moving east across NSW has seen a man killed by a fallen tree, with thousands of others left without power after heavy rain, winds and lightning recorded across the state.

The elderly driver has not yet been formally identified, but it is believed his car was struck by a falling tree at about 3:50pm on Lachlan Valley Way, between Cowra and Gooloogong.

At the time, the Bureau of Meteorology reported Cowra's wind gusts to be around 117kph. Wind gusts of 120kph were recorded at Trangie west of Dubbo and 113kph at Cabramurra.

Traffic was diverted away from the scene, with drivers and emergency services personnel clearing roads of fallen trees and debris.

Another four people were injured in Wagga Wagga when high winds ripped off the roofs of demountable huts.

NSW State Emergency Service crews have received more than 2250 calls and responded to more than 1800 incidents in 24 hours, predominantly for fallen trees and property damage.

More than 120,000 residents have been left without power and 300 electrical hazards are causing concern across the state.

Severe thunderstorms will combine with a low-pressure weather system, expected to bring up to 80mm of rain until Saturday, the Bureau of Meteorology has warned.

Friday will see the worst of the rain, with up to 100mm predicted in some areas.