Emergency alert signals — sirens, phone alerts, what to do

Official warnings reach you through several channels on purpose. Ready.gov states the goal plainly: when emergencies strike, public safety officials use timely and reliable systems to alert you. Plural, because any single channel has a way of failing — the power is out, the phone is in another room, you are asleep, the network is congested. Layered alerting is how a warning survives one of those going wrong.

This guide covers what those layers are, what they can and cannot tell you, and what to do in the first minutes after one goes off.

One caveat shapes everything below. Siren tone patterns are not internationally standardized. A rising and falling tone that means "take shelter" in one country can mean a drill, a fire department callout, or nothing at all in the next one over. The only authoritative source for what a siren means where you live is the table published by your own country's civil-protection or emergency-management authority. This guide will not guess at any country's tones — instead it shows you how to find yours, and covers the layers that do work the same way nearly everywhere.

The layers, briefly

Ready.gov describes the pieces of the United States system, and the shape is recognizable in many countries even where the names differ.

Phone alerts. Wireless Emergency Alerts (WEAs) are short emergency alerts authorities can send to any WEA-enabled mobile device in a locally targeted area. In the US, the authorities allowed to send them include state, local, tribal and territorial public safety officials, the National Weather Service, the National Center for Missing and Exploited Children, and the President.

Broadcast. The Emergency Alert System (EAS) is a national public warning system that lets the president address the nation within ten minutes during a national emergency, and lets other authorized alerting authorities deliver weather information, imminent threats, AMBER alerts and local incident information targeted to specific areas. It travels over broadcast TV and radio, satellite digital audio services, direct broadcast satellite providers, cable television and wireless cable systems. Ready.gov notes that it is also used when all other means of alerting the public are unavailable.

Weather radio. NOAA Weather Radio All Hazards is a nationwide network of stations broadcasting continuous weather information from the nearest National Weather Service office, based on your physical location: official warnings, watches, forecasts and other hazard information, 24 hours a day, seven days a week. It also carries non-weather emergencies through the EAS.

The backbone. The Integrated Public Alert and Warning System (IPAWS) is FEMA's national system for local alerting. It lets public safety agencies send WEAs, EAS alerts and weather and non-weather messages simultaneously through NOAA weather radios and, in Ready.gov's own words, alerts through systems like sirens and digital billboards. IPAWS alerts can be locally targeted so only devices in the affected area receive them.

That last line is the useful one for sirens: a siren is an output of an alerting system, not a system of its own. Someone local owns it and decides what its tones mean.

Sirens — the layer that varies most

Because sirens are locally owned, their meanings are locally defined. There is no global convention to memorize, and the worst thing you can do is carry a pattern you learned somewhere else into where you live now.

Two things are nonetheless true of outdoor sirens almost everywhere.

The first: a siren is an attention signal, not an instruction. It cannot tell you what happened or what to do. Its entire job is to make you go and find the message — on the radio, on your phone, from local officials. Treating the sound itself as the information is how people end up guessing.

The second: outdoor sirens are built to be heard outdoors. Inside a well-insulated building with the windows shut, you may not hear one clearly, or at all. That is not a fault in the system; it is why the phone and broadcast layers exist alongside it.

So find your own table, once, and be done with it:

• Start with your national civil-protection or emergency-management authority. Where a country uses sirens for public warning, that agency normally publishes the signal table — how many tones there are, how long each lasts, and which one means the alarm is over.
• Ask your municipality or local emergency management office which sirens actually cover your address, and when they are tested.
• Note the test schedule if there is one. Knowing that the sirens sound on a fixed day at a fixed time removes most of the fear from hearing them.
• Write down what you find and keep it where the household can see it. A signal table you have to search for during an emergency is not a signal table.

If you cannot find such a table, treat that as an answer too: sirens are probably not how your country warns the public, and the phone and broadcast layers below are the ones to get right.

Phone alerts — the layer that finds you

Phone alerts are the closest thing to a universal layer, and the details Ready.gov gives for WEAs describe how cell-broadcast warning works generally.

They look like text messages, but are designed to get your attention with a unique sound and vibration repeated twice. They are not affected by network congestion and will not disrupt texts, calls or in-progress data sessions. You are not charged for receiving them, and there is no need to subscribe — no sign-up, no app, no account. Children receive them on their own devices too, which Ready.gov flags as a reason to talk to them about what the alerts are before one arrives.

If you have never received one, Ready.gov's troubleshooting is worth five minutes: check the settings on your device and your user manual, since some phone models require you to enable the alerts and older phones may not support them at all. Some carriers label the setting "Government Alerts" or "Emergency Alert Messages" rather than anything about emergencies. If it still does not work, ask your carrier.

Outside the United States the mechanism is the same even when the branding is not. In the European Union, Article 110 of the European Electronic Communications Code required member states, by 21 June 2022, to ensure that where public warning systems for imminent or developing major emergencies and disasters are in place, public warnings are transmitted by mobile providers to the end-users concerned. A country may instead use another electronic communications service or a mobile app, provided the system is equivalently effective at reaching people — including those only temporarily in the area — and the directive adds a plain requirement that public warnings shall be easy for end-users to receive. Note the condition in that first sentence — the obligation applies where such a system is in place, so it is not a guarantee that every country has one. The useful homework is finding out whether yours does and what it is called.

One honest caveat while we are here: no app sends official alerts, ours included. Warning the public is a government function, and a preparedness app can only hold what you prepared in advance.

What to do when an alert arrives

Ready.gov's sheltering guidance sets the priorities, and the first one covers every case: stay informed and follow the instructions of local authorities.

Then, if the instruction is to shelter in place:

• Bring your family and pets inside.
• Lock doors, close windows, air vents and fireplace dampers.
• Turn off fans, air conditioning and forced air heating systems.
• Go into an interior room with few windows if possible.
• Take your emergency supply kit with you — a packed bug-out bag is exactly this, ready in advance.
• Pay attention to local media outlets for official news and instructions as they become available.

Set your expectations honestly on that last point. Ready.gov says it outright: local authorities may not immediately be able to provide information on what is happening and what you should do. The first minutes after an alert are often quiet. That is normal, and it is not a reason to go looking for answers on the street.

Keep the phone network free while you are at it. Mobile networks can become overwhelmed during emergencies, making it hard to make and receive calls; text messages need less bandwidth and get through more reliably when everyone is trying to use their phone at once. Text rather than call, and keep the battery for the alerts. If the power is out as well, the power-outage guide covers the radio and charging side of it.

Your family rally plan

Alerts arrive at inconvenient moments, and Ready.gov builds its whole planning advice on that fact: your family may not be together when a disaster strikes, so know how you will contact one another and reconnect if separated, and establish a family meeting place that is familiar and easy to find.

Ready.gov's plan starts with five questions worth answering out loud, at a table, once:

• How will I receive emergency alerts and warnings?
• What is my shelter plan?
• What is my evacuation route?
• What is my family or household communication plan?
• Do I need to update my emergency preparedness kit?

Then adjust for who is actually in your household — different ages, medical needs and prescriptions, disabilities and the devices that go with them, languages spoken, pets or service animals, school-age children, and the places people go every day. And do the step most households skip: practice the plan with everyone in it.

The layers at a glance

None of this needs to be memorized. Learn the two or three signals your own authority publishes, find out what a phone warning looks like before one arrives, agree on a meeting place with the people you live with, and the next alert becomes an instruction to follow rather than a puzzle to solve.