My group went up on 5/22 and made it up to Trail Camp. Did not summit the next day since a couple people form my group got hit hard by the altitude. At night I feel like it was under 20 degrees as our 20 degree sleeping bags were barely adequate. My water bottle in the tent had ice in it when I woke up.
There is snow that needs to be crossed once pass mirror lake but crampons weren't necessary to get to Trail Camp. Didn't see anyone using the switch backs.
There was water that can be filtered at trail camp.
