Fabric curtains stretch across the huge Warragamba Dam to trap ash and sediment expected to wash off wildfire-scorched slopes and into the reservoir that holds 80% of untreated drinking water for the Greater Sydney area.

Smoke haze and poor air quality caused by wildfires temporarily suspended practice sessions for the Australian Open at Melbourne Park on Tuesday, but qualifying began later in the morning in "very poor" air quality.

Thunderstorms and showers brought some relief for firefighters battling deadly wildfires across Australia's drought-parched east coast on Wednesday, but also raised concerns that lightning will spark more fires before dangerous hot and windy conditions return.

More than 50 homes were damaged or destroyed and 13 firefighters were injured overnight by catastrophic wildfires across Australia's most populous state before the emergency subsided on Wednesday, officials said.