Yosemite National Park's elevations range from 4,000 to 8,800 feet. Yosemite's high mountain country means the air is dry and thinner. (There is less oxygen in the air.) Visitors who are coming from lower elevations will notice this, particularly when exerting themselves on a hike or other outdoor activity. Some may experience discomfort from altitude-related ailments. Symptoms include headache, nausea, insomnia, irritability, shortness of breath and/or general fatigue. The best way to prevent these unwelcome symptoms is to gradually acclimatize yourself to the area's higher elevations during your first one or two days in the area. Even for visitors who are not hiking, it's important to know that Tioga Pass is situated at about 10,000 feet elevation.

Despite its tall mountains and meadows, Yosemite National Park can be a hot place in the summer. And, the heat can ruin your Yosemite vacation experience if you don't take precautions. If you have asthma, diabetes, a heart condition, knee or back problems, or any other health or medical issue, limit both your exertion and your exposure to the heat. The altitude, strenuous climbing, dehydration, and intense inner canyon heat will combine to make any medical problem worse. Stay within your physical limitations, and abilities. Read more on Preventing Heat Illnesses and Tips for staying cool on boiler days.

The heaviest items in your pack should be food and water. The heat, as well as the steep trails this area offers, will sap your energy, and you need to stay well hydrated and well fed. Salty snacks and water or sports drinks should be consumed on any hike lasting longer than 30 minutes. (Remember this mantra: No food = No fuel = No fun.)

Wear good footwear. Many of the trails in the Yosemite region are steep, loose and exposed. There is little, or no, margin for error on many of the available hiking trails. As a result, wear sturdy footwear that has good support and provides exceptional traction.

If you're exploring when you see lightning, go to low-lying areas away from cliff edges, lone trees, poles, or metal objects. Make sure the area is not subject to flash floods. Do not seek shelter in caves or alcoves.

Become a smaller target by squatting low on the ground. Place hands on knees or back of neck with head between knees. Do not lie down or touch the ground with your hands. Minimize contact with the ground and nearby rocks to minimize ground current effects caused by a nearby strike.

Wild animals are just that - wild. Although some wild animals appear to be docile and tame, they are wild and unpredictable.

Keep your distance from animals, even if they approach you. One way to help prevent/avoid a surprise encounter with wild animals is to dispose of trash in animal-proof trash cans or dumpsters. This is especially important in bear country.

Black bears inhabit the Yosemite region and human food scents, poor storage, etc., can serve as an attractant. Encounters serve to threaten your safety, and also does harm to the bear. If a bear, or other wild animal becomes attracted to a non-natural food source, it will become habituated and frequent areas popular with people.

Please see this page for more information and links about proper food storage during your trip to Yosemite.

In Yosemite National Park, failure to obey regulations may result in a fine of up to $5,000 and/or impoundment of your property.