FROST damage can occur in foothill vineyards in Spring and in Fall, and should be a consideration when choosing a vineyard location and appropriate varieties.
Rick Snyder, UC Biometeorology Specialist, has training units, available in English and Spanish here on his website.
Active Frost Protection: Water
Active Frost Protection: Wind Machines
Passive Frost Protection
Methods of Measuring Temperature
Rick Snyder's handouts from his "Frost Protection" presentation as PDF FP_GrapesColor
Links from Rick's website: