A severe weather warning is in place for the Sydney, Hunter and Illawarra areas, with the Bureau of Meteorology warning damaging winds could reach up to 90km/h this afternoon.


Trees have fallen across roads and traffic lights are out across the city after the winds hit earlier today.


The State Emergency Service has already received 140 calls for help and "they are still rolling in", spokeswoman Sue Pritchard said. Most have been for fallen trees are those threatening to come down.


Power is out to about 30,000 homes and business around Hornsby and Berowra.


Traffic lights are out on Pennant Hills Road between Waitara and Normanhurst and there are three sets of traffic lights out on Seven Hills Road, near Baulkham Hills.


Snow is also predicted overnight in the NSW Snowy Mountains region.