I voted summer. Actually, it is anytime the weather is decent.
My hubby make a walking trail around our land, so we walk it (it is 1 1/2 miles) morning and evening. Plus, we are avid outdoors people, so we are always hiking, camping, canoeing, etc. Winter time, sometimes here, it can be so cold or icy, so we don't get out much during the winter....we do play fetch, etc. in the house though.