MONROE - Although much of the northern half of Wisconsin has experienced colder temperatures and accumulating snow the past week, the Association of Wisconsin Snowmobile Clubs wants to remind snowmobilers that most snowmobile trails in Wisconsin are not open yet. Before a trail can be opened, the ground under the snow needs to be frozen to ensure trails crossing wet areas are safe. In agricultural areas, adequate snow is necessary to protect the ground and crops over which the trail travels.