With wading, it's hard to target crappies. They have to come to us, in a sense. We sometimes see them surfacing and we'll tie up a jig and float it. We typically wade for walleye or bass and if we get lucky enough to see them school, we'll target them.
Best bet for crappies is a boat and hit the onion fields or red cross areas. As far as the weather, if you can get to them, you could probably get them to bite. The cold rain might chase them to deeper waters, unless they are on nests already.
Someone else probably knows more, like I said, we don't target them too often.