Drug crop exposed during Adelaide winds

More than 40,000 Adelaide properties are without power and a hydroponic drug crop has been exposed after overnight strong winds brought down trees, branches and power lines.

Police are warning motorists to take extra care on the roads, saying the city's eastern suburbs and foothills have been hit hard but reports have come in from across South Australia.

They say a cannabis hydroponic set-up was exposed after a tree crashed into the roof of an unoccupied Glen Osmond home late on Monday night.

Neighbours rang authorities after becoming concerned that a glow coming from the roof cavity was a fire.

But the glow was found to be strong lights linked to a cannabis-growing room.

Police are seeking the home's owners or its occupants.

The State Emergency Service has been busy with hundreds of calls from people affected by the strong winds, including jobs involving trees falling on houses and cars.