Motorcyclist dies in wet Sydney crash

A motorcyclist has died after colliding with a B-double truck on a major road in Sydney's northwest during torrential conditions.

Emergency services could not revive the motorcyclist when they were called to Pennant Hills Road in Carlingford about 7am on Thursday, police say.

Multiple lanes remain closed, causing significant delays across the wet morning commute and motorists are advised to avoid the area.