In California state every driver is charged with acting with due reasonable care depending on the conditions of the roadway. So if a driver loses control of their vehicle and causes a collision with your vehicle, such as a rear-end accident, the fact that the roads were icy and covered with snow is not a defense for them on your case—they may still be responsible for the damage to your vehicle and your injuries.  

Remember, the measuring tool for this "due reasonable care." Thus, if an accident happens due to icy road conditions because another driver lost control, more likely than not, there was a negligent reason from the other driver for this happening.  Such as unsafe speed or an unsafe turing movement.   In San Diego, the freezing temperatures are not as common as compared to other parts of the state.  However, it does dip into freezing on occasion especially in the mountains and back parts of San Diego County near Julian.