Sparkslingers - Cloud City, #1

Deret Day's got spark. Lots of it. He always knows exactly what to do. It's been his gift for as long as he can remember, and it makes him stand out in his dreary little town of Median. But it's not until he is mysteriously led to find an even more mysterious book about clouds, that his "just fine" life is headed for so much more. Recruited into an atmospherically diverse team of other Sparkslingers, Deret's natural spark-slinging abilities lead him into a turbulent world in the clouds where Dusk Dragons, Storm Ponies, and countless other magical creatures abound.
There, he discovers what really goes on in the sky to make weather happen. Charged with the responsibility of maintaining balance on Earth against a spark-stealing, black fog called sludge, the Sparkslingers team must intervene to restore balance and save Median. They'll just have to survive the most epic storm in a generation to do it. /'spärk/: The vital force that nourishes and propels life; the inner element within all living things that initiates drive, desire, and longing; that which makes one want.