Severe thunderstorms left a man injured and cut power to at least 7000 homes in Sydney's northern outskirts, hitting the Hawkesbury area hardest.
A 65-year-old man was airlifted to Westmead Hospital after suffering head injuries when a tree fell through his farmhouse at Freemans Reach on Reserve Road.
CareFlight, SES volunteers, paramedics and police responded to the incident, freeing then treating the man who was in a stable condition.
Emergency crews patrolled the area and have been working to restore power.
A high chance of rain has been forecast in Sydney for the rest of the week, with the possibility of thunderstorms every day.
The Bureau of Meteorology has forecast a cloudy, rainy day for Christmas with a thunderstorm likely in the afternoon and evening, while temperatures are expected to hit 28 degrees.
