A decent packable puffy is a good thing to have - it is unlikely that you'll use it but I won't go without one now. As mentioned pretty much anything can happen in the high country and it can quickly turn from 60 and sunny to winter.
We got caught on a camping trip between 10 and 11k in elevation where it went from 65 and sunny to 37 and sleet. It was August and we were not prepared for winter weather. Luckily we were on the way in, threw up the tent, waited out the storm then made the defeated hike back to the truck to get off the mountain and warm. When we got home and checked the weather it had gone down to 29. Would have been a baaaad night. Forecast called for 60s and sunny with a slight chance of afternoon rain.