From the nice folks at the National Weather Service, via the new Weather.com Dashboard widget:

259 PM PST FRI NOV 24 2006 ...Frost advisory in effect from 2 AM to 8 AM PST Saturday...

The National Weather Service in San Francisco has issued a frost advisory…which is in effect from 2 AM to 8 AM PST Saturday.

Further drying was expecrienced today as dew points continued to drop across much of the Salinas Valley. Relatively clear skies tonight combined with low dew points will allow overnight lows to tumble into the upper 20s and lower 30s. Areas of frost will likely develop as several hours of near freezing temperatures are experienced.

A frost advisory means that frost is possible. Sensitive outdoor plants may be killed if left uncovered.