Miyuke Harwood was lost in the rugged Sierra Nevada for nine days last August, her leg broken from falling off a cliff. She’d left the group she’d been hiking with to return home early. Rescuers’ chances of finding her alive looked bad. But the veteran 62-year-old hiker survived. The item authorities credited with saving her life? A whistle.

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Her voice, weakened by days of starvation and pain, couldn’t reach far enough to summon searchers, but her whistle could.

This light, tiny piece of equipment is one of the heavyweights of hiking safety, recommended by trail guides and the National Park Service. Yet too few people think to invest the $2 or so it costs. Putting it on a lanyard around your neck can be especially helpful; if you are separated from your backpack, the most essential emergency item, aside from water, is right with you.

Spring brings the start of warm-weather hiking, a delight with its wildflowers and longer, sunlit days, but also a potential danger. Most hiking mishaps happen during warm weather — partly because more people are hiking, but partly because warmer weather raises the risk of dehydration and heat stroke and brings out certain natural risks, such as poison oak and poison ivy.

As the author of a hiking guide and a certified naturalist and hike leader, credentialed in wilderness first aid, I’m often asked about the dangers of mountain lions and rattlesnakes. Though they do exist in the wilderness areas where I live, in Southern California, I’ve never been harmed by one, nor have any of the dozens of other naturalists I know. Only one of them has even seen a mountain lion in the wild.

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The bigger danger, I always tell people, is you, if you’re unprepared for the wild. Aside from a whistle, here are a few items to be sure you pack to protect yourself from the far more likely hazards of spring and summer trails.

Water. Yes, it’s obvious, but no matter how much people are warned, failure to carry enough water is the single biggest problem on the trail. Water not only prevents dehydration, it can be used to help cool a person suffering from heat exhaustion, rinse off after treating poison-oak exposure and clean wounds. A pint for a five-mile hike is far too little, yet you’d be surprised, when I ask hikers to show me their water before we start, how many show me one little bottle. Bring at least two quarts for such a hike.

Shade hat. Another one that seems obvious yet few bother bringing. The protection it provides from the sun, especially on ridgelines and other exposed areas, can be the wall between you and heat exhaustion, a possible precursor to heat stroke. Baseball caps aren’t the best protection because they fit closely to the head, which means the heat can penetrate through the cloth to the head, and because they have a brim on only one side. A shade hat of any kind is better. Don’t forget sunscreen, too.

Related: Heat Exhaustion and Heat Stroke: Spot the Symptoms

Rubbing alcohol. Spring and summer are when poison oak and its close relatives poison ivy and poison sumac are growing along the trails. Learn to identify them, and wear long sleeves and pants if hiking in infested areas. But sometimes, contact can’t be avoided. At those times, the University of California Integrated Pest Management Program recommends isopropyl alcohol to remove the urushiol, the oil in the plants that provokes a rash in most people. You can bring a small bottle of regular rubbing alcohol, or bring, as I do, individually packaged alcohol prep wipes, sold in pharmacies. They’re lightweight and take almost no room. Rinse the area with water afterward, UC Davis advises.

Related: 7 Poisonous Plants to Avoid

Cold packs. In hot weather, a cold pack can be used to provide basic comfort, or emergency care in case of heat exhaustion or heat stroke, applied to pulse points such as the armpits and groin. It also can be used to reduce swelling for sprains and wounds. The kind that turn cold when smacked hard are lighter than freezer packs and always ready to turn cold when you need them.

Cooling scarves. These little necktie-looking scarves contain water-absorbent gel beads that expand and cool when soaked in water for a couple of minutes (another great use for that extra water you brought). They weigh practically nothing and are so small you can stick them in any little crevices of a backpack. They don’t get as cold as cold packs, but they can help prevent heat-related problems and discomfort when draped across the neck or tied headband-style across the forehead.

Duct tape. A great all-round hiking companion, it can be used to make impromptu bandages with fabric, fashion a splint with a stick, repair broken equipment, close up the cuffs of pants or shirts in tick territory or even provide a quick fix for busted hiking shoes. Just ask Cheryl Strayed, author of “Wild,” how useful duct tape can be. She fashioned booties for herself out of duct tape when she lost one of her hiking boots on the Pacific Crest Trail. The Washington Trails Association recommends it as a fix-it for many trail problems.

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Karin Klein is a California-based journalist covering health, science, education and food policy. For 26 years she worked as an assigning editor and editorial writer for The Los Angeles Times.