The waterfowl migration movement is when birds move from breeding grounds in the north to the south during the fall season. Waterfowl are protected by federal laws, so the U.S. Fish and Wildlife service determines the hunting season based on migration patterns.
Hunting season lengths are set by the USFWS based on the movement of the waterfowl to the wintering grounds in the south. Excessive research is required for a successful state-monitored hunting season. According to the research, migrations are getting later each year, as of 2015.
Since hunting is a popular pastime for many, some are willing to travel extensively to hunt. It's very likely that the weather affects the outcome of the hunting season, since the timing, length and capacity of the waterfowl migration depends on the weather.