It happened shortly before 1 a.m. on Highway 101 near De Long Avenue.
The Highway Patrol says the driver of an SUV lost control when the vehicle was hydroplaning through a stretch of wet road and rolled over several times.
The driver was not wearing a seat belt. She died at the scene.
An infant and a 3-year-old child riding inside the vehicle were able to get out of the SUV on their own.
They were taken to two different hospitals with unknown injuries.