The land leases for the private property that many of the trails run through expire the last day of March. You can still ride on many of the trails in the Hills after that but the trails through private lands close the last day of March. Good riding in the Hills is usually done well before that but varies. Trail grooming has already become sporadic and they will probably give it up completely quite soon. Too warm to groom trails and after the first rainy day it is done. Trail groomers do not work very well or at all in wet snow. The temperature outside needs to be in the mid 20s anyway. Also if it is not cold enough overnight for the groomed snow to "set up" it is a waste of time.