Hiking weather and mountain safety

How to read a mountain weather forecast

A town forecast says little about conditions on a ridge. Use a mountain or hill forecast where one exists, and look at:

• Temperature at height. Air typically cools by around 6 to 7°C for every 1,000 m you climb, often more on a dry day. A mild 15°C in the car park can be near freezing on a high summit, before wind chill.
• Wind speed at summit level. Walking gets tiring in sustained winds of around 50 km/h (30 mph) and difficult or dangerous above that, especially on exposed ridges.
• Cloud base. If the summits are in cloud, you'll be navigating in poor visibility.
• Freezing level in spring, autumn and winter. Above it, expect ice and snow.
• Thunderstorm risk and timing.

Thunderstorms and lightning on the hill

In many mountain ranges, summer thunderstorms build in the afternoon as the day heats up. Timing is the best protection: when storms are forecast, start early and plan to be off summits, ridges and open high ground by early afternoon.

Warning signs include towering cumulus clouds that grow quickly upward, darkening cloud bases, sudden gusts and cooling, and thunder of any kind. If you can hear thunder, you're close enough to be struck.

If a storm catches you

• No place outdoors is safe. The aim is to reduce the risk while you get lower.
• Get off peaks, ridges and high open ground quickly. Head down into a valley or thick, uniform forest of similar-height trees.
• Avoid isolated trees, rock overhangs and shallow cave mouths, open water, and metal such as fences and cables.
• In a group, spread out at least several metres apart so one strike can't injure everyone.
• If you can't get lower and strikes are very close, crouching on your pack or a sleeping mat with feet together, keeping contact with the ground small, is a last resort. It reduces the risk only slightly; getting to lower ground matters more.
• Wait about 30 minutes after the last thunder before returning to exposed ground.

Hiking in heat

Heat exhaustion shows as heavy sweating, weakness, headache, nausea, dizziness and cramps. Stop in shade, rest, cool the person with water and fanning, and give fluids. Confusion, collapse or hot dry skin may mean heat stroke, which is a medical emergency: call for help and cool the person as fast as possible.

To prevent it, start early, rest in shade during the hottest hours, drink regularly, eat salty snacks, and wear a hat and loose, light clothing.

Cold, wet and windy weather

Hypothermia isn't only a winter risk. Rain and wind at 5 to 10°C is enough when people are tired and underfed. Early signs are shivering, clumsy hands, stumbling, mumbling and poor decisions.

• Put on layers before you get cold.
• Get out of the wind, add dry insulation and a waterproof shell, eat something sweet, and keep moving downhill if you can.
• If someone stops shivering but is still cold and confused, they're getting worse. Get help.

See boots and layers for a clothing system that copes with this.

When to turn back on a hike

Turning back is a skill, and good hikers do it often. Turn around if:

• You reach your turnaround time.
• Thunder, building storm clouds or stronger wind than forecast appear.
• Anyone in the group is struggling, cold, unwell or injured.
• The terrain is harder than you expected, or there's snow and ice and you lack the equipment and skills.
• Visibility drops and you aren't confident navigating in poor visibility.

What to do if something goes wrong

1. Stop, make the area safe and keep the group together.
2. Protect the casualty from the cold and the ground with spare clothing and your emergency shelter.
3. Work out your location: grid reference, coordinates from your phone, or a clear description.
4. Call 112 in Europe or 911 in the US and Canada (or the local number). In some countries you ask for mountain rescue or the police. If calls fail, a text may get through; in the UK you need to register your phone for emergency SMS in advance.
5. Stay where you said you'd be, and keep your phone on while saving battery.

Mountain weather safety FAQ