The trail was covered with snow from the parking lot (and all the way to the summit). Crampons weren't necessary but micro spikes were, along with trekking poles. This was probably the most difficult trail of the six to climb for several reasons, the first being the (often deep) snow covering the entire trail, and another being crevasses that were opening up. I haven't felt cold like I did at Camp Muir in a long time. Bring a coat, hat, gloves, neck gaiter, and other things to shield yourself from the frigid weather. When heading back down, the weather turned bad really quickly. Visibility was poor because of the whiteout, which made navigating the snow covered trail next to impossible. Extra precautions needed to be taken in order to avoid falling into a crevasse or off a cliff. Take a GPS with you! If I would have had the option to wait until later in the summer when most of the snow was gone, I would have.