The Great Sand Dunes, and most of the forests, lakes and peaks of Great Sand Dunes National Preserve, are designated wilderness. These areas can be explored by day hikes or overnight backpacking trips. View of the 30-square-mile dunefield and Sangre de Cristo Mountains from highest dune on the first ridge. NPS Photo. Explore any part of the 30 square mile dunefield you wish; there are no designated trails in the sand. A dunes-accessible wheelchair is available for free loan at the Visitor Center. Summer air temperatures are pleasant at this high elevation, but during afternoon hours the sand surface can reach 150F degrees, and dangerous thunderstorms can develop. Plan to hike the dunes in early morning or evening to avoid heat exhaustion, burned feet, or fatal lightning strikes.