Southbound I-5 closes at Grapevine Road while the northbound lane closes near Highway 138.
VIDEO: Snow piling up as the Sierra gets hit hard
Caltrans officials say they do not have an estimated time for reopening.
"The Grapevine is closed due to dangerous conditions. Caltrans is working hard to make it safe. We will open it as soon as possible," California Highway Patrol Grapevine Tejon wrote on social media.
PHOTO GALLERY: Snow shuts down Grapevine