Yosemite National Park is a United States National Park and a UNESCO World Heritage Site located in the Sierra Nevada mountains in east-central California
. Yosemite is internationally recognized for its spectacular granite cliffs, waterfalls, clear streams, giant sequoia groves, and biological diversity. The 750,000-acre, 1,200 square-mile park contains thousands of lakes and ponds, 1600 miles of streams, 800 miles of hiking trails, and 350 miles of roads. It is currently the third most visited national park in the United States, with an annual visitation of nearly 4 million.
Yosemite is best known for the massive granite cliffs and domes found within the park. The landscape began forming about ten million years ago when the Sierra Nevada was uplifted and then tilted to form its relatively gentle western slopes and the more dramatic eastern slopes. The uplift increased the steepness of stream and river beds, resulting in formation of deep, narrow canyons. About one million years ago, snow and ice accumulated, forming glaciers at the higher alpine meadows that moved down the river valleys. Ice thickness in Yosemite Valley may have reached 4,000 feet during the early glacial episode. The downslope movement of the ice masses cut and sculpted the U-shaped valley that attracts so many visitors to its scenic vistas today.
The park is also home to the Yosemite Falls, at 739m (2425ft), the highest waterfall in North America.
» Flora and fauna
Yosemite has more than 300 species of vertebrate animals, and 85 of these are native mammals. Black bears are abundant in the park, and are often involved in conflicts with humans that result in property damage and, occasionally, injuries to humans. Visitor education and bear management efforts have reduced the bear-human incidents and property damage by 90% in the past few years. Ungulates include large numbers of mule deer. Bighorn sheep formerly populated the Sierra crest, but have been reduced to only a few remnant populations. There are 17 species of bats, 9 of which are either Federal or California Species of Special Concern. Over 150 species of birds regularly occur in the parks. Other species that are found within the park include bobcat, gray fox, mountain beaver, great gray owls, white-headed woodpeckers, spotted owls, golden-mantled ground squirrel, martens, Steller's jays, pika, yellow-bellied marmot, white-tailed hare, and coyotes.
The vegetation in the park is primarily coniferous forest. Most notable among the park's trees are isolated groves of giant sequoias, the largest trees in the world, which are found in three groves in Yosemite National Park.
Weather can change rapidly during all seasons of the year, and will also vary greatly with elevation. When visiting it is wise to pack for any season with clothing that can be layered, ready to peel off or add on as conditions dictate. Always include some kind of rain gear; the park receives most of its precipitation in the months of January, February and March, but storms are common during the transitional spring and fall seasons, and spectacular thunderstorms may occur during summer.
For Yosemite Valley and Wawona (subtract 10-20°F (5-10°C) for Tuolumne Meadows), average weather is as follows:
Summer: Typically dry, with occasional thunderstorms; temperatures from 50°F (10°C) to the low 90°F (30°C) range.
Fall & Spring: Highly variable, with typical high temperatures ranging from 50-80°F (10-27°C) , with lows from 30-40°F (-1 to 4°C). Rain is less likely early in fall/late in spring and rain or snow is likely late in fall/early in spring.
Winter: Snowy, rainy, or (sometimes) even sunny days are possible, with highs ranging from 30-60°F (-1 to 16°C) and lows in the high 20°F (-4 to 0°C) range. Winter Storm Warnings indicate a significant storm is impending or occuring.