Flagstaff has never reached 100 degrees. The temp differential is huge during the drier atmospheric times though mid 30's to 80 might be about the extent of the diurnal swing.

Edit: a residential area just outside of the town limits at a slightly lower elevation and down slope from the mountains will hit the very low 100's on the hottest days. It is where 2 large forest fires hit earlier this year. 100°, and windy at 6,800 feet elevation is not comfortable.