Nice time to hike around the Merced Grove or take the trail down to the Tuolumne Grove. For fewer fellow travelers, take the trail into the Merced Grove. Lunar rainbow may be visible at base of Lower Yosemite Fall. Dogwood trees and western azalea bushes bloom in moist areas. Monarch butterflies return, some after a 1,000-mile migration from Mexico.
Female mosquitoes hatch.
Striped coral root, a delicate saprophytic member of the orchid family, flowers in the forest. I've seen these along the Old Big Oak Flat Road heading down toward the Tuolumne Grove. You can also find them in August along the moist forested trail between Sentinel Dome and Taft Point. Mid May Showy red snow plants push their way up through the decaying humus of the forest floor. This is an unusual looking plant and may take you by surprise.