Two kinds of hikers. Only one still knows what to do when the screen goes dark.

Apple's support pages say iPhones are designed to work between 32° and 95°F. In colder conditions, battery life temporarily shortens and the phone may turn itself off. Anyone who has started a hike on a frosty morning has probably watched a battery fall faster than the trail map suggested it should.

The satellite SOS page is just as direct. You need a clear view of the sky and the horizon, and trees, hills, mountains and canyon walls can all block the connection. Even with a clear view, Apple notes that a single message can take minutes to get through.

Two kinds of hikers read that fine print differently. The first group treats the phone as the backup and assumes it will work when it matters. The second group takes Apple at its word and carries a backup that doesn't depend on battery temperature, tree cover or a patch of open sky.

A 2026 study in Wilderness & Environmental Medicine surveyed more than 600 visitors to Rocky Mountain National Park. The researchers checked what people were carrying and what plans they had made, then measured both against a standard for being wilderness prepared.

The results were low. Only 15.7% of day hikers and 25% of trail runners met the standard, which included carrying a map or another navigation tool. About a quarter of the people surveyed hadn't told anyone their route before heading out that day.

The second kind of hiker clears that bar with two habits. First, a non-digital reference rides in the pack, so navigation and first aid don't depend on a screen staying lit. They also tell someone where they are going and when they expect to be back. Neither habit costs much time or money, and both appear on the checklist the researchers used to score everyone else.

The pages that matter most on a trail are the ones you can follow without a connection. The handbook covers navigation without a compass, reading weather signs, signalling and being found, and first aid. It also includes color plates of edible and poisonous plants for identification in the field.

Everything is written in plain language and backed by step-by-step illustrations. You can follow a knot, a shelter build or a ground-to-air signal by looking at the drawing, which helps when your hands are cold and your attention is split between the page and the weather.

The full Third Edition is a substantial hardcover, and that is worth knowing before you plan to carry it. A common habit is to keep it sealed in a zip-lock bag, either in the pack for longer trips or in the car at the trailhead. Either way, the plan is on paper and within reach when the screen goes dark.