Hotter the better! This is why tropical fruit trees should be planted in the worst time of year! 

Most plants can tolerate between 20-120 degrees, if given proper water, and maintaining a healthy root system. 99 percent of plant related problems in the desert, are directly linked to water, humidity, and moisture. Deserts are the hottest and coldest places to live, and can all be controlled by water. This is why flood irrigated properties are the best to have here, but very unaffordable, given water is always a concern here.