Quite a few years ago I was riding in a competitive trail ride when a thunderstorm blew up. We were out on trail with no shelter nearby. Many people who are close to lightning strikes report a strange smell and I never believed that until I experienced it that day. The deafening crack of thunder spooked both myself and my horse. Knowing that sitting up on a steel shod horse made me a great lightning rod was rather un-nerving.

If possible you shouldn't ride during thunderstorms. But if the unavoidable happens your About Guide to Sports Medicine, Elizabeth Quinn, offers advice for Lightning Safety. And Safe Horse Riding in a Storm from Petcaretips.net has good advice about horses and storms.