im planning a summer trip to south san juan wilderness for a backpacking/flyfishing trip.

anyrate my question is how does elevation effect temperature, Ive found that the night time low average for a town close to the area is 48f in july, the town is at 7,890ft. im planning to be around 10-11k durring my trip. so with that information what ballpark should the temp be?

Thanks for the help! if you cant tell im sleeping bag shopping