Summer is the most popular time for hiking in the Sierra Nevada.
In summer, you may encounter extremes in temperatures from winter-like cold to high heat and humidity, along with rapid changes in the weather. You may associate hypothermia only with winter; however in the mountains hypothermia can be an issue year-round. That is why it's important to have warm, waterproof clothing with you no matter what it's like when you start your hike.

Summer's heat can create problems for hikers, including:

• Heat exhaustion, which will leave you feeling tired, nauseous, dizzy, and headachy. Rest, rehydration and a good night's sleep are the treatment for heat exhaustion.
• Heat stroke is a life-threatening illness. Symptoms include confusion, delirium and loss of consciousness. The skin feels hot as the body's cooling mechanism fails. THIS IS A TRUE EMERGENCY. Cooling the patient immediately is essential.
• Asthma and other respiratory conditions may be triggered by heat. Have all appropriate medications.

Both heat exhaustion and heat stroke can be prevented by avoiding overexertion on hot days. Pace yourself, rest often and drink plenty of water throughout your hike. You'll know that you've drunk enough water if your urine is "clear as mountain spring water."

Summer's storms can create problems for hikers, including:

The Sierra Nevada can enjoy extended periods of superb weather with crisp nights and pleasant sunny days. Seldom are there extended periods of rainy weather but late afternoon thunderstorms are common. Adequate clothing and shelter is a must.

• Hypothermia can result from becoming wet and cold when you don't have adequate wet weather gear. Watch your companions to make sure they are not developing hypothermia.
• Lightning can occur out of a clear sky but is usually associated with storms. It can be both exciting and nerve racking to have thunder and lightning bouncing off the peaks around you. Avoid open meadows and exposed peaks and ridges during summer storms.
• Read more about Wilderness Safety here.