The CHP's Bakersfield office announced the shutdown shortly before 5:30 a.m. Caltrans announced lanes were reopened with California Highway Patrol escorts around 3:41 p.m.
CHP later stopped escorting drivers, but advised the public to go below the 65-mph speed limit.
The northbound side of the 5 was closed at Parker Road in Castaic, while the southbound side was closed at Grapevine Road.
Just after 6:30 a.m., Caltrans said the so-called "snow gate" would be opened to allow northbound traffic to make a U-turn southbound.
Highway 58 through Tehachapi was open and suggested as an alternate route.
Malibu mud and rock slides forces closure of Highway 23 at PCH, Caltrans says
An image tweeted by the Highway Patrol at 7:22 a.m. appeared to show vehicles moving in a single lane on the freeway, but it was unclear what time the photo was taken and in which direction the vehicles were traveling.
While frigid conditions gripped the Grapevine, other parts of Southern California were being soaked on Thursday.
As of 10:30 a.m., the highest precipitation total in the region was at Cogswell Dam in the Bobcat burn scar area of the San Gabriel Mountains, where 7.08 inches of rain was recorded, according to the National Weather Service.
In the San Gabriel Valley, Monrovia Canyon Park remained closed as a precaution due to fears of possible mudflows. K-rails remained in place near homes in the immediate area.
"You just don't want anything to break and you don't want people to lose their houses if the mud slides off the mountainside there," said resident Nancy Tinker, who braved the rain to go for a jog. "Getting stuck in mud is not fun."