The National Park Service urges SPECIAL CAUTION for all hikers during the summer months.

Every year, scores of unprepared hikers, lured by initially easy downhill hiking, experience severe illness, injury, or death from hiking in the canyon.

Be aware that efforts to assist you may be delayed during the summer months due to limited staff, the number of rescue calls, employee safety requirements, and limited helicopter flying capability during periods of extreme heat. If you need to be rescued, you will be charged for rescue expenses.

Do not rely on physical strength alone, hiking intelligently will take you much farther. Rangers take heat exhausted hikers to the hospital every day during the summer.

Be sure to check the Backcountry Updates and Closures page for current information on trail conditions and situations affecting the backcountry.

YOU SWEAT AROUND 1/2 TO 1 QUART OF WATER AND ELECTROLYTES FOR EVERY HOUR YOU WALK IN THE HEAT.

This fluid/electrolyte loss can even exceed 2 quarts per hour if you hike uphill in direct sunlight and during the hottest time of the day. Because inner canyon air is so dry and hot, sweat evaporates instantly, making its loss almost imperceptible.

Do not wait until you are feeling thirsty to start replacing fluids and electrolytes. By the time you feel thirsty, you are already dehydrated. Even a mild level of dehydration can make hiking a lot less fun. The more dehydrated you become, the less efficient your body becomes at walking and cooling.

Your body can only absorb about 1 quart of fluid per hour, so drink ½ to 1 quart of water or sports drink every hour that you are hiking in the heat. Carry a water bottle in your hand and drink small amounts often.

Balance your food intake with fluid consumption, else you run the risk of becoming dangerously debilitated and severely ill. Food is your body's primary source of fuel and salts (electrolytes) while hiking in the canyon. Eat a salty snack every time you take a drink.

AVOID HIKING BETWEEN 10AM AND 4PM!

Even if you are eating and drinking correctly you still need to avoid hiking in direct sunlight during the hottest part of the day. Sun temperatures are 15F to 20F (9C-11C) degrees higher than the posted shade temperatures. And keep in mind, the lower you go the hotter it gets!

Plan your day so you are not hiking between the hours of 10am and 4pm. Take a break near shade and water to avoid the worst heat of day. Enjoy a predawn start and a late afternoon finish. Experienced desert hikers know that the timing of their hike is the most important factor in avoiding hazards. Almost all the people who need emergency medical help in the canyon due to heat illness are hiking between 10am and 4pm.

When hiking out, do not hike uphill in direct sunshine. Your body will use a lot of energy trying to stay cool. Because you sweat out more water and electrolytes hiking in direct sun you dramatically increase your risk of developing a heat-related illness. Always bring a lightweight flashlight to give yourself the option of hiking out after dark in the event that illness, injury, or enjoyment should slow you down.

KEEP YOURSELF SOAKING WET TO STAY COOL.

This is one of the best things that you can do for yourself. Whenever you are near water, make sure that you wet (actually soak) yourself down. If you hike while soaking wet you will stay reasonably cool. This will make a wonderful difference in how well you feel, especially at the end of the day!

WATCH OUT FOR THESE HEALTH HAZARDS!

HEAT EXHAUSTION - The result of dehydration due to intense sweating. Hikers can lose one or two quarts (liters) of water per hour. Rangers at Phantom Ranch and Indian Garden treat as many as 20 cases of heat exhaustion a day.

Symptoms: pale face, nausea, cool and moist skin, headache, cramps.

Treatment: drink water, eat high-energy foods, rest in the shade, and cool the body.

HEATSTROKE - A life-threatening emergency where the body's heat regulating mechanisms become overwhelmed by a combination of internal heat production and environmental demands. Grand Canyon has two to three cases of heatstroke a year.

Symptoms: flushed face, dry skin, weak and rapid pulse, high body temperature, poor judgment or inability to cope, and unconsciousness.

Treatment: the heatstroke victim must be cooled immediately! Continuously pour water on the victim's head and torso, fan to create an evaporative cooling effect, move the victim to shade, and remove excess clothing. The victim needs evacuation to a hospital. Someone should go for help while attempts to cool the victim continue.

HYPONATREMIA (water intoxication) - An illness that mimics the early symptoms of heat exhaustion. It is the result of low sodium in the blood caused by drinking too much water and losing salt through sweating.

Symptoms: nausea, vomiting, altered mental states, and frequent urination.

Treatment: have the victim eat salty foods. If mental alertness decreases, seek immediate help!

HYPOTHERMIA - A life-threatening emergency where the body cannot keep itself warm, due to exhaustion and exposure to cold, wet, windy weather.

Symptoms: uncontrolled shivering, poor muscle control, and careless attitude.

Treatment: put on dry clothing, drink warm liquids, warm victim by body contact with another person, protect from wind, rain, and cold.

Avoid hypothermia by checking at Canyon View Information Plaza or Backcountry Information Center for latest weather and trail conditions, taking layered clothing for protection against cold and wet weather, eating frequently, replacing fluids and electrolytes by drinking before feeling thirsty, and avoiding exposure to wet weather.