Over the next few days we will see significant change. We could see all four seasons between now and Friday. In our forecast, a strong low pressure system will move across Northern Arizona. Our chances for rain run from tonight through Friday. We could see thunderstorms on Thursday evening as the core of the system moves through our region.
Temperatures will progressively decline. Many places will have their first freeze of the season on Friday night. I think Saturday night could be quite cold, too.
If you check the NWS Flagstaff Weather story, in the right hand sidebar, you see their graphic which nicely explains the situation.