BART trains are running slowly this morning due to the cold weather, transit officials said early Thursday.

Passengers are advised to add an additional 20 minutes to their planned travel times.

The National Weather Service issued a freeze warning for parts of the Bay Area, including the Sonoma Coastal Range, North Bay Interior Mountains and North Bay Interior Valleys. The Sonoma Mountains could see snow at 1,000 feet, and the weather agency reported that the valley floor may see some snow, too.

A frost advisory was in effect this morning for San Francisco, the Marin Coastal Range and Coastal North Bay, including Point Reyes National Seashore and the San Francisco Bay Shoreline.

Snow enthusiasts should check out our list of the closest spots to catch some flakes.