The Buffalo Storm — Katherine Applegate

Hallie isn't afraid of anything--that is, anything but storms, which she braves along with her grandmother, huddled beneath a special quilt. When her family decides to join a wagon train and go west, leaving her grandmother--and everything Hallie has ever known--behind, Hallie knows she will have to be braver than she's ever been before. Then one day on the trail she witnesses the wildest, most glorious storm imaginable. How can she be afraid of anything after that?
Lyrical text from an exceptional writer is paired with gorgeous, jewel-like paintings in this evocative story of westward expansion.