UPDATE: The teen who died while hiking near the Three Sisters trail has been identified as Yasmen Vidales. An 18 year-old, female who resided with her parents in San Diego. The original story follows-
San Diego County CA– On July 22, at 4:13 pm, Julian Deputy Sheriffs responded to Boulder Creek Road, Julian for a medical aid assist call at the Three Sisters Falls trailhead. A female adult hiker reported her eighteen year old female hiker companion was suffering from heat related physical distress.
Deputies arrived at the same time as the fire department and first aid was started immediately. The victim was airlifted to a local San Diego hospital where she was eventually pronounced deceased.
The Three Sisters trail is rated a medium to difficult hike
The American Hiking Society has some tips for hiking in hot weather:

• Wear clothes that wick moisture away from the body (avoid cotton).
• Use sunblock – SPF 15 or higher is recommended. Apply prior to going outside.
• Soak your bandana in cool water and place it on your neck or head and the evaporation will cool you.
• Actually, jump in the water with your clothes on (not hiking boots and socks – use water shoes) and hike while wet to stay even in cooler!
• Get your head wet too, but don’t ingest any untreated water.
• Plan an early start for your hike, when the day is cooler, and plan so that you’re walking in more shaded areas during the hottest part of the day.
• Stay hydrated. Drink lots of water or, if you’re on a long hike, a sports drink with electrolytes.
• Hike more slowly.

Signs for knowing heat related problems are happening to you or someone you are hiking with:
For your own safety and the safety of those with whom you’re hiking, know what heat exhaustion and heatstroke look like and know what to do:
Heat Exhaustion:
Symptoms: pale face, nausea, vomiting, cool and moist skin, headache, cramps. (Don’t ignore a headache when hiking in hot weather! This is serious stuff. Stop. Drink. Rest.)
Treatment: drink water with electrolytes, eat high-energy foods (with fats and sugars), rest in the shade for 30-45 minutes, and cool the body by wetting it with cool water. If nausea or vomiting prevent drinking fluids, get the victim to a hospital as fluids may need to be administered intravenously.
Heat stroke – This is a life-threatening emergency
Symptoms: flushed face, dry skin, weak and rapid pulse, high core body temperature, confusion, poor judgment or inability to cope, unconsciousness, hallucinations, seizures. Sometimes symptoms of heat stroke can mimic those of a heart attack or other conditions.
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. Immerse the victim in cold water if possible. Move the victim to shade and remove excess clothing. The victim needs to be evacuated to a hospital. Someone should go for help while attempts to cool the victim continue.