Check the weather: In the high country, a bright summer day can turn stormy within minutes, with lightning, high winds and even snow. In the Rocky Mountains, thunderstorms typically develop in the early afternoon.

Get out early: If hiking, start your hike early in the day - and plan to be down the mountain by noon. Summer thunderstorms can form quickly anytime in the afternoon. Get below treeline or to safe shelter before a storm strikes.

Stay alert: If you hear thunder, lightning is close enough to strike you. If you see lightning in the distance, it's close enough to strike you. And at altitude, if skies look threatening, a thunderstorm can develop immediately. A significant lightning threat generally extends up to 10 miles from the base of a thunderstorm cloud. And on rarer occasions, bolts can strike up to 15 miles from a thunderstorm.

Above treeline: Get away from summits, isolated trees and rocks. Find shelter but avoid small cave entrances and rock overhangs. They won't protect you. Crouch down on your heels.

Below treeline: If you are in a forest, stay near a lower stand of trees. Stay away from tall, isolated trees or other tall objects.

What's safe shelter: Tents, trees, small caves and picnic shelters are not safe. A vehicle or a substantive, enclosed building are. Stay away from water and any metal.

Essentials: Carry these: rain gear, map and compass, flashlight or headlamp, sunglasses and sunscreen, matches or other fire starter, candles, extra food and water, extra layers of clothing, pocketknife and a first aid kit.

The Associated Press