Vermont is the kind of state that experiences a sudden influx of senior citizens in the warm, summer months, and then quickly clears out after the leaves hit the ground. Every non-profit organization in the Green Mountain state would do well to keep this trend in mind. The winter volunteer base of every organizaiton will be cut in half at least due to the migration of many to the south. In addition, ice and snow will keep another part of your volunteer force off the roads.
This will lead to an unpredictable schedule for your volunteers and your expectations must bend according to their availability. If you have a mailing to go out, have it ready at least a week before it must go out. Allow some flexibility for the volunteers. If one can come in during a Tuesday morning, but another can come in on Thursday afternoon, let them come in as they will instead of losing them for the sake of concentrating them into one time slot. The winter is not the time to be picky about when you can and cannot have help.