Stormy, Misty's Foal - Marguerite Henry

Misty is a Chincoteague pony mare who is close to foaling, and the Beebe family is anxious about it. Unfortunately, a terrible storm system arrives first, setting up over Chincoteague with floods, hurricane winds, ice, and snow.

The story is fictional, but is based on historical characters, human and equine. Stormy describes events on Chincoteague Island during the Ash Wednesday Storm that hit the Eastern Seaboard March 6, 1962.

This is the sequel to Misty of Chincoteague by Marguerite Henry (Summary adapted from Wikipedia)