Afternoon thunderstorm The typical weather pattern is for a brief thunderstorm to move in each afternoon. Be prepared by stowing a rain shell in your pack and making sure you’ve descended from high, exposed ridgelines by early afternoon.

An early start  See “Afternoon thunderstorm.” Leave yourself plenty of time to descend from exposed peaks or ridges before a storm hits. If you’re planning a hike of six or seven miles round-trip, say, you’ll want to hit the trail by 8 a.m.

High-altitude temp Pack a fleece or a lightweight but warm synthetic layer, especially if you’re taking a chairlift or gondola to your hike; avoid wearing cotton, which stays cold when wet and contributes to hypothermia, a consideration even in the summer. Temps atop Eagle’s Nest, for example, can be a good ten degrees colder than at the base.

Adequate water Stay hydrated, especially at higher altitudes, with water that you’ve brought. If you’re hiking with a pooch, make sure you bring extra wet stuff, and a bowl, for your friend; dogs can easily be overcome by heat exhaustion, especially on sunny afternoons. Water in lakes and streams carries a risk of giardia, a nasty intestinal parasite, so don’t drink from them unless you’ve thought ahead and brought a way to treat it.

Adequate food The more strenous the hike, the more calories you’ll burn. Pack an energy bar to stoke your furnace, and an extra in case your trip should last longer than anticipated.

Emergency shelter Buy a space blanket or bivvy, which weighs almost nothing and folds into the size of a handkerchief, and tuck it in your pack. You’ll be glad you did if you need it.

Orientation Know where you’re going before you leave the trailhead. All local outfitters sell area trail maps, so buy one, and take it with you. Having a handheld GPS receiver in your pack is always a good idea, since many trails lead into cell-phone dead zones where Google Maps and Siri won’t be able to assist you, should you lose your way.