Clear skies, light winds, cold air mass cause frost overnight

SAN DIEGO - Clear skies, light winds and a cold air mass caused frost in the inland valleys of San Diego County early today, according to the National Weather Service.

A frost advisory that went into effect in the inland valleys at midnight was scheduled to be in effect until 8 a.m.

During the advisory period, temperatures fell into the upper 20s near Ramona and the San Pasqual Valley. Many other areas dipped into the lower 30s, according to the weather service.