Thunder Spring Trail

The Thunder Spring Trail is the most rewarding moderate hike in Palomar Mountain State Park, traversing the high-country forests and meadows of one of San Diego County's most beloved mountain escapes. The 3.5-mile loop explores the varied terrain of Palomar Mountain's protected interior, passing through dense stands of white fir, incense cedar, and black oak before descending to Thunder Spring, a reliable water source that supports a lush riparian zone within the otherwise dry mountain landscape.

Spring is the most spectacular season to hike this trail, when an exceptional variety of wildflowers blooms throughout the forest understory and in the small clearings along the route. Crimson snow plant, white-flowered Solomon's seal, blue ceanothus, and numerous woodland lilies create a succession of color from April through June that draws botanically minded hikers from across the region.

The high-country forest of Palomar Mountain exists as an ecological island, isolated from similar mountain communities to the north and south by lower desert terrain, and supports plant and animal communities found nowhere else in San Diego County. Mountain lions, mule deer, and a rich diversity of birds including several woodpecker species inhabit the forested slopes along this route. With 500 feet of elevation gain across 3.5 miles, the loop is well within reach of hikers of moderate fitness. The $10 per vehicle park entry fee applies. Leashed dogs are welcome. Visitors should be prepared for rapidly changing mountain weather and carry rain gear in all seasons.