Plucking the strings of temperature depended on just how extreme the ambient temperature began. Teasing a cold night colder didn’t require as much effort as reversing the thermometer. Most weather wizards could easily beckon heat into a chilly day over an hour or two, with minor concentration. To thrust the heat into the air required greater skill: not only did it require more energy, but you risked burning or nipping yourself. After all, the change came from a willful thought.