Even in the dead of winter in the sierras, 10 degrees, I would burn up in anything heavier than a LS capilene 1, a LS Capilene 3 and a windshirt if its really windy. Yes, I start a little cold but I quickly warm up. In the evening (summer) the capilene 3 is all I need for warmth on top on the Cap 1. BUT, I tend to hike from "can see till can't see" so I do very little sitting around getting cold. (This burned me on a recent winter trip when I went with a group and it was short mileage days and a good bit of idle time.)
Net, I have gradually whittled down my extra clothes after dozens of sierra trips. Two years ago I hiked the JMT in 9 very long days. Your hiking style may be completly different and clothing requirements.
Whatever you take, you're in for a great experience. Great time a year for the trip.
