Hello. I was backpacking in Yosemite this past weekend, 5/17. The original plan to reach Upper Cathedral Lake was thwarted by the snow on the trail, and so only managed to reach Lower Cathedral Lake. All in all, it was a fun trip. I will post pictures later today.
For the first 2 miles, the trail is dry. In the next 1.5 miles, above 9000', the trail was covered in snow up to 4' thick. In some places it is packed and one can easily walk on it, but in other spots it is soft and one will sink. The trail was covered in snow for most of the way and showed little traffic. At times the trail disappeared and split off in various directions where people had tried to find it. A lot of backtracking and cross-country navigation was involved reaching the lake.
The last half mile from the junction to the lake took us 2 hours. The trail was buried in snow at this point, and we stayed close to the creek on the south side following the trail on the map and trying to avoid as much of the snow melt as possible. The area is full of streams with snow melt, precarious snow bridges, and a lot of snow. At the edge of the lake, the snow was pretty much gone. We camped on the north side of the lake. There were plenty of dry spots in between the trees.
The temperature throughout the day was in the mid-60s with clear skies. At 4am, the temperature was 40F. It was dry throughout the day and night, but the wind was blowing all night long. The trees provided protection around camp, and you could hear the wind howling over the lake and through the open areas. We saw only two other people camping on the granite slab on the east shore of the lake.
On the way out, to avoid the snow we encountered on the way in, we exited on the north side of the creek paralleling for most of the way until reaching the main trail. This time we reached the junction in 30 minutes and with dry feet. Snowshoes, hiking poles with baskets, gaiters, and/or micro-spikes would be useful depending on your level of adventure.