When severe weather strikes, the warning may come from several places at once.
A loud outdoor siren might sound across a neighborhood. A smartphone may blare with an emergency alert. Television programming may suddenly be interrupted by a tornado warning.
Some emergency managers say that overlap is intentional. Research shows people are more likely to notice and respond to danger when warnings come from multiple sources.
That conversation is gaining attention locally as officials in Ann Arbor ask residents for feedback on whether the city should retire its outdoor warning siren system.
Why experts recommend multiple warning systems
Studies on disaster communication show that people rarely receive severe weather alerts from just one source.
A federal investigation by the National Institute of Standards and Technology following the devastating 2011 Joplin tornado found that many residents first became aware of danger through one alert such as a siren or television broadcast. Many then sought confirmation through other sources like smartphones or news coverage before taking shelter.
Researchers concluded that warnings are often most effective when several systems reinforce the message.
People frequently look for confirmation before acting, meaning the same warning delivered through multiple channels can help prompt faster responses.
Who outdoor sirens are designed to reach
Despite common assumptions, outdoor warning sirens were not designed to wake people inside their homes.
The National Weather Service says sirens are primarily intended to alert people who are outdoors.
That could include children playing in the yard, runners on neighborhood streets, people walking dogs, construction crews or crowds gathered at outdoor festivals and sporting events.
When sirens sound, the goal is to get attention quickly and prompt people to seek shelter and check additional information sources such as television, radio, smartphones or weather radios.
A real-world example in Ann Arbor
Ann Arbor’s outdoor sirens have been activated only twice in the past five years, according to the city. One of those times occurred during the Ann Arbor Art Fair in July 2023, when severe weather threatened thousands of people attending the outdoor festival.
Large events like the Art Fair illustrate the type of situation outdoor sirens were originally designed for. With large crowds outdoors and many people not watching television or checking weather apps, sirens can serve as a mass alert telling people to seek shelter and look for additional information.
Ann Arbor officials say removing the sirens would not mean eliminating emergency warnings. Instead, the city would rely on several modern alert systems. These include Wireless Emergency Alerts, which automatically send warnings to compatible cell phones within a defined geographic area during life-threatening emergencies. The city also operates A2 Emergency Alerts, an opt-in system that can send notifications by text message, email or phone call. Officials say those tools can deliver more detailed instructions, reach residents in multiple languages and target alerts more precisely than outdoor sirens.
City leaders say the review is also intended to evaluate how people receive information today. Ann Arbor officials say their analysis considers public safety effectiveness, the clarity of emergency messaging and the responsible use of public funds when maintaining aging infrastructure.
Still, emergency management research suggests different warning systems often reach people in different situations, which is why many experts recommend using several alert methods together.
The growing role of smartphone alerts
Modern technology has added powerful tools for warning the public.
Wireless Emergency Alerts are designed to override silent mode and produce a loud tone and vibration so people notice them.
Wireless Emergency Alerts have also improved in recent years. In 2019, the system was upgraded through the Federal Communications Commission and the Federal Emergency Management Agency. Message limits expanded from 90 characters to 360 characters, allowing emergency managers to provide more detailed information about a threat. Improvements to geographic targeting also help ensure alerts reach phones closer to the actual warning area.
Why phones still may not reach everyone
Even with those improvements, smartphones do not always reach every person at risk.
Phones may be left inside homes or vehicles. Batteries may be dead. Some people, including young children or certain older adults, may not carry phones.
People who are exercising outdoors, working outside or attending events may not notice alerts immediately.
Because of those limitations, emergency management agencies such as the Federal Emergency Management Agency recommend combining several warning systems rather than relying on one.
Another important tool: NOAA Weather Radios
Emergency managers frequently recommend NOAA Weather Radios as another reliable way to receive warnings.
These devices receive alerts directly from the National Oceanic and Atmospheric Administration (NOAA) and the National Weather Service.
Weather radios are designed to sound an alarm automatically when alerts are issued, even overnight while people are sleeping.
For many emergency planners, weather radios remain a dependable way to receive severe weather alerts.
Siren policies vary across communities
Across Michigan and the country, communities have taken different approaches to tornado sirens. Some cities maintain large outdoor warning systems, while others have reduced or eliminated them because of aging infrastructure or maintenance costs.
In parts of Kalamazoo County, for example, siren coverage varies from township to township. Some areas removed sirens years ago, while at least one community, Comstock Township, has recently discussed bringing them back after residents raised concerns about how people outdoors would be warned during severe weather.
How everyday life affects how warnings are received
How warnings reach people often depends on what they are doing when severe weather strikes.
A child playing outside may hear an outdoor siren first.
A runner on a trail might notice the warning tone from a smartphone alert.
Someone asleep overnight may rely on a weather radio alarm to wake them up.
Families watching television may see a weather alert interrupt programming.
Emergency managers say these everyday scenarios illustrate why multiple warning systems are often used together, since each method reaches people differently depending on their environment and daily routine.
Research on disaster communication suggests there is no single warning system that reaches everyone.
Instead, experts say safety often comes from redundancy. Multiple alerts delivered through different technologies help ensure that when severe weather strikes, more people receive the message in time to take action.
Add to the ways that you receive alerts by downloading the 4Warn Weather app here.