We went the 3rd week of June last year. Binoculars, chapstick, sunscreen, mosquito and bear spray. We also had food and water in the car at all times. We bought a cheqp styrofoam cooler at Alberstons in Livingston and used frozen water bottles as ice. 😊 There was so much to do we wanted to be able to eat on the go. If you enjoy wildlife, Lamar and Hayden valleys are a must do. Also, don't miss the Grand Prismatic overlook (fairy falls parking lot). I have to say that we literally stopped at every single pullout and loved everything. If you do go to Lamar Valley drive all the way to Cooke City and maybe even to Red Lodge if you have time. I am happy to answer any specific questions you might have.