Warnings on your phone: setting up cell broadcast and warning apps

A phone is always connected to a cell, meaning the area served by a particular mobile mast. With cell broadcast, the network operator sends a message on behalf of the authorities to selected cells all at once. Every compatible device there receives it, whoever owns it and whatever country its SIM card comes from. It is more like a radio station than a text message.

The advantage: a text message has to be sent to each number separately. When everyone is calling at the same time, such individual messages get stuck in a queue. Cell broadcast needs no individual connections, so it usually still gets through when the network is heavily loaded. The authorities also do not need to know anyone's phone number.

Warning apps work differently: they fetch their messages over the internet. In return they can do more, for example warn you about saved places. That way you hear about a storm heading for your parents' town even though you are somewhere else. The two routes complement each other.

Take a calm look at your phone's settings once. Depending on the device the section is called something like ‘emergency alerts’ or ‘wireless emergency alerts’. There you can see which warning levels are switched on. Depending on the country, some levels cannot be switched off at all, others can. Do not switch anything off lightly just because a sound annoyed you once.

Keep your phone's software up to date, because warning features are improved through updates. Check elderly relatives' devices too: very old or very basic phones may not support cell broadcast. A battery radio is then a good addition.

A warning is not a news article to read later. It contains instructions. Read it to the end and act on it, without first waiting for a second confirmation on social media.

Phone warnings depend on two things: the mobile network and the battery. If the power is out for a long time, mobile masts can eventually fail too. That is why authorities recommend a mix of warning channels: phone, warning app, radio, sirens, loudspeaker announcements. Any single channel can fail; together they are reliable.

Find out what the siren signals in your area mean, and keep a battery-powered or wind-up radio ready. During major incidents the radio often broadcasts more detailed information than fits into a short phone message.

When you receive a warning, also tell people near you who may not have a phone, may hear poorly or may not understand the language – neighbours or children, for example.

Many countries hold regular test alerts; Germany, for example, has a nationwide warning day. Use such days as a free test: did the message reach you? Your children, parents, grandparents? If not, check the settings together.

When travelling, cell broadcast usually reaches your phone too, but often in the local language. Find out in advance which warning systems your destination uses and whether there is an official warning app. Note the local emergency number; in the EU it is 112.

Real warnings cover things like severe weather, floods, wildfires, hazardous substances in the air or major power cuts. Typical instructions are: go indoors, close windows and doors, switch off ventilation, avoid or leave an area, turn on the radio.

In the EU, public warning systems via the mobile network are required; many countries implement them as cell broadcast. In the USA the phone warnings are called ‘Wireless Emergency Alerts’ and run through a system of the federal emergency agency FEMA. The names in the settings therefore differ from country to country.

A common misconception is that cell broadcast needs location services or mobile data switched on. That is not necessary, because the message simply goes to the cell. Warning apps, on the other hand, need internet and, if you want warnings for your current location, usually location permission too.

The loud alert tone may be startling. It is designed that way on purpose – partly so that people wake up at night.