2 yrs ago, I went on a 1 wk bus trip with guild. The temp was below 80, overcast, nice wind. Since it's upper dessert, it's more likely to be be very hot, dry, dusty. We went to the store on Friday. Stayed in Bend. Returned on Saturday before 8:00am. For lunch, I purchased a sandwich from a restaurant at 11:00am and got a snack in the pm.
It was worth it, but I'm not planning to attend this time.
I suggest you take: hat, water, sun glasses, sun screen, very comfortable shoes, fan, shopping bag.