This is what I was told when I asked why we didn't shoot year round.
Nov and Dec are out as most of our shooters are out hunting deer, we always got a very poor turnout in those months. Our various deer seasons (archery, BP, rifle, etc.) start normally in mid to late Oct and end around the last part of Jan.
Jan and Feb we normally get a lot of ice storms here. The range is located on John Zink Ranch which is private property and the ranch itself lacks equipment to clear the roads into our range during winter weather. There are two very steep ridges to get over to get to our range and they become impassable with any ice on the roads. As I understand it, the shooters were polled and since we had so many matches cancelled due to bad weather in Jan and Feb, the decision to start the Matches each year in March was made.