Sully, IMHO the most beautiful place on earth! The last time the DW and I went there was Mid October 2009, and all I can say is WOW! It was 65* to 70* when we were there during the day, and it snowed in the high country every night. All the roads were plowed and snow free during the day. The Elk (Bulls) were bugling and fighting right at the Mammoth Hot Springs Ranger Station. Almost all the animals we seen there were in the North End of the Park. All the Fall colors were beautiful as well. Have fun and enjoy your trip!