SAN DIEGO - A frost advisory was in effect early Friday in San Diego County's valley areas, which, along with the deserts, were expected to have below-freezing temperatures Friday.
The National Weather Service issued a frost advisory for the valleys until 8 a.m. and a more serious freeze watch for both the valleys and the deserts from this evening through Saturday morning, saying temperatures could drop to around 25 to 30 degrees Friday.
The drop in temperatures is due to a cold air mass and gusty northwesterly winds, according to the weather service. The agency said wind gusts throughout San Diego County Friday would be around 30 to 40 miles per hour.
"The winds will make driving difficult, especially for motorists with high profile vehicles," according to an NWS advisory. "Watch for broken tree limbs and downed power lines."
The Mountain Empire Unified School District in East County canceled classes Friday due to hazardous road conditions.
Elsewhere in the county, high surf and coastal flood advisories remained in effect early Friday for the beaches, where 6 to 10-foot waves were occurring since early Thursday. The weather service said both advisories would remain in effect until 11 a.m. Saturday.
For mariners off the coast of San Diego County, a small craft advisory was scheduled to remain in effect through late tonight. A small craft advisory means that wind speeds of 21 to 33 knots and combined seas of 10 feet or greater are expected to produce hazardous wave conditions for smaller boats.
Other areas of Southern California were impacted by the cold weather.
The Grapevine section of the Golden State (5) Freeway was reopened early Friday, but only with California Highway Patrol escorts, after having been closed about 4 p.m. Thursday due to snowy conditions, according to Caltrans.