LOS ANGELES (AP) -- Southern Californians awoke Thursday to record cold with sub-freezing temperatures in the mountains and deserts, but forecasters said a slight warming trend was on the way.

Overnight frost advisories were in effect until midmorning for the mountains, valleys and some coastal areas.

The temperature dipped to 14 degrees in the high desert town of Lancaster Thursday morning, breaking a 2006 record low of 15 for the date, the National Weather Service said. Neighboring Palmdale had 21.

Many other areas reported lows in the 30s and 40s. Los Angeles and San Diego hit 43.

The community of Ramona in San Diego County had a low of 45, tying a 1991 record for the date.

A lack of cloud cover can allow temperatures to drop rapidly overnight without a blanket of clouds to seal in warmth, and forecasters said areas of frost were possible through Thursday night in some coastal areas, valleys and lower deserts.

A slight warming trend was expected later in the day through Friday, with Los Angeles and many other areas seeing highs in the low to mid-60s.

For Friday night and Saturday, a weak cold front will bring a chance of rain, and a more potent cold front could bring additional rain Sunday night and Monday, according to the National Weather Service.

The AP.