Yosemite National Park
Yosemite's waterfalls are at their most spectacular in May and June. When the snow starts to melt (usually peaking in May), streaming snowmelt spills down to meet the Merced River. By summer's end, some falls, including the mighty Yosemite Falls, trickle or dry up. Their flow increases in late fall, and in winter they may be hung dramatically with ice. Even in drier months, the waterfalls can be breathtaking. If you choose to hike any of the trails to or up the falls, be sure to wear shoes with no-slip soles; the rocks can be extremely slick. Stay on trails at all times.
Visit the park during a full moon and you can stroll without a flashlight and still make out the ribbons of falling water, as well as silhouettes of the giant granite monoliths.