I have found, in Toquerville, that I can successfully plant, during the summer months, many garden items I could not successfully plant in climates a bit warmer in the summer. Such things as cucumbers, beets, melons and squash. In warmer climates these have to be planted in the spring before the summer heat stresses them out of production. And in colder climates they must be planted in early spring just to be able to mature before cool weather arrives in the fall. But the summers are mild enough in Toquerville that most plants don't stress as they do in St George or southern Nevada. Plus the growing season is long enough that the plants can mature and produce before cold weather arrives.
I believe the key to this is the fact Toquerville is protected from the morning sun until at least 8 a.m. during the summer, and the fact that the daily high temperature is almost always reached by 2 pm and immediately begins to cool from that hour. The Toquerville high, on average, is 3 degrees cooler than St George, but that high is maintained for a far shorter period of time than St George. Also, I have observed that shortly after sundown, Toquerville will be from 10 to 15 degrees cooler than St George--even though both cities may sometimes reach the same night time low, Toquerville will reach that low much earlier in the evening than does St George.
This weather pattern means that plants, which begin to stress at temperatures above 100 degrees, will be stressed for only a relatively short period of time in Toquerville, but for a much longer period of the day in St George and other southern, desert areas.