Will I need to rejet my Rancher for this winter i live in central illinois and bought it back in august

 

Unless you have added a pipe or filter or made any airbox alterations, I wouldn't think you'd need to rejet even though cold air is denser & requires some changes in sport or performance quads. Most utility quads are in a mild state of tune and more forgiving.
Having said that, only your engine can tell you what it wants as to air/fuel mix, so doing a plug read is simple & the final answer.