I'm not sure if there's a legitimate scientific study on the subject, but my observations have been that deer move regardless. They're going to move in rain, even moderate to heavy rain. I killed a nice buck in a downpour two years ago. Saw several deer that day. I've had several other days with many deer sighted in moderate rains too. I don't see many deer in the south in any kind of significant snow event though. They seem to shut down.