Phone signal in the mountains and national parks: how to plan for the gaps

Why it comes and goes on the same path

Mobile signals work best in a clear line between the phone and the mast. Ofcom, the UK telecoms regulator, lists hills, buildings and trees between you and the mast among the things that affect reception, and a UK government study notes that valleys and hills reduce the area a rural mast can cover. Worcestershire County Council's advice adds that heavy tree canopies block the connection, and that outdoors, the thing to do is head toward higher ground.

Masts also follow people. The same council notes that areas with lower commercial returns, such as rural settlements, are more likely to have poor coverage. In practice that means signal near villages, roads and ski areas, and long stretches without it on the trails in between. A path that drops into a gorge can lose everything in a few minutes and get it back on the next shoulder.

Maps: the offline trap for walkers

An offline map is the first thing to download, but check what it can do. Google says that when you are offline, walking, cycling and transit directions are unavailable in Google Maps, and only driving directions work from a downloaded area. The map and your position still show, so you can follow a path you already know, but the app will not plan a walking route without data.

Apple Maps behaves differently: as our guide to Apple Maps offline explains, Apple says a downloaded area keeps directions for walking as well as driving, cycling and transit, where the feature is available. Whichever you use, plan the route at home, save it, and download a wide area around it, since directions only work offline inside what you saved. Your position comes from satellite positioning, which keeps working without mobile signal, as covered in calling for help with no signal.

Battery is the real limit

A phone in and out of coverage spends the day searching for a network, which uses battery whether or not you touch it. Apple's advice for low-signal areas is to turn on Airplane Mode. In the mountains, that can be the default between villages: the map and your position still work, and you turn data back on at a viewpoint to send a message.

Cold adds to it. Apple says the drop in battery life in very cold conditions is temporary and recovers when the battery warms up, so keep the phone in an inside pocket rather than the outside of a rucksack. Carry a battery pack on any day where the phone is your map. Our article on battery drain while travelling has the power-saving settings for iPhone and Android.

Borders on the ridge

Mountain ranges are often borders, and the phone does not see them. In the Pyrenees, the strongest mast on a high pass can be Andorran or French; in the Alps, Swiss, Italian, Austrian or French. That matters for the bill. Switzerland and Andorra are outside the EU roaming rules, so a usual line with data roaming on can be charged for a few minutes on their networks; see our guides to roaming in Switzerland and to Andorra and the microstates.

With a travel eSIM, check the plan against the range you are walking. Snoozim's Europe pack includes Switzerland but not Andorra, which has its own plans. A single-country pack stops at its own border, even on the ridge, so near a frontier it may simply drop until you are back on a network of its country.

Before you set off

• Tell someone your route and when you expect to be back, and agree what they do if you do not check in.
• Send that check-in from the last place with signal, not from the summit you hope will have it.
• Learn where your phone shows coordinates and how to read them out.
• Know how your phone handles emergencies with no network at all, including satellite SOS on recent models.

In the EU, 112 is free to call from fixed and mobile phones and reaches the same services as each country's own numbers. Our guide to calling for help with no signal covers coordinates, automatic location and satellite SOS in detail, and using your phone on a ski trip covers the winter side of the same mountains.