You are right, a cold front will normally send them to the bottom in the thickest brush they can find. It is no different during the spawn. But the good news is, the females are staging in those areas anyway, so they will be in the same places they were before the front. As I said, it MAY be a little tougher to get them to bite if the water temp changes a lot due to a cold rain, but the main factor will be water clarity, muddy water will have the worst affect on the bite. JMO. If the water is clear, it will be fine.