Late may the animals are starting to drop their calves. You may get lucky and encounter a bear in Grand Teton. Trumpter swans, blue heron, osprey, and bald eagles are some of the larger birds you will encounter. Weather is unpredictable at that time of year. Bring clothing for both winter and warmer weather conditions.
Early morning is very cold but can warm up in the afternoon.
Layering is the best advice. The lodge has tours through the park, but not sure when they open for the season. Your information will be helpful. I am so excited. Almost wish time would move along, but one must be careful for what they wish.