It's actually pretty warm all day, we start with a long T-shirt and a windproof jacket and bring two more T-shirt in my backpack, then I take off the jacket just hike with my long T-shirt, it get a little chill near mirror lake, then I put back my jacket, then just hike with my jacket for the rest trail, I don't use the extra T-shirt at all, so I think you should check out the weather at summit, if it's not super windy or cloudy, I think T-shirt and one more windproof jacket should be fine.
