Too Cold

It would be too cold in some areas. Beartooth highway would be closed. There would be snow at places. I was at Tower-Roosevelt early this month, and it was below freezing point at night. Mammoth and Old Faithful areas were OK.

Unless you have a four season tent with good sleeping bags, forget about it.

One time I spent 3 days in the park in early May, it was also chilly. I think for a casual traveller, the best time is 6/10~9/10.