Tornado Siren Simulator

Play the real outdoor warning siren — the wailing "attack" and steady "alert" tornado tones

Press Tornado below to hear the classic outdoor warning siren, then use Play Sound and the controls to shape the wail. The simulator is preset to the tornado "attack" pattern — a slow, rising-and-falling tone built to carry for miles. It is for education and demonstration only and is not an emergency alert system.

Tornado & Warning Sirens

● Ready — Tornado
Waveform

Frequency Controls

500 Hz 900 Hz

Modulation Controls

0.1 Hz

Sweep Controls

0.1 Hz

Sound Shaping

15% 2% 50%

What Is a Tornado Siren?

A tornado siren — more precisely an outdoor warning siren — is a high-powered public warning device mounted on a pole or rooftop and operated by a city or county emergency management agency. When a tornado warning is issued, or when trained spotters report a tornado, officials activate the sirens to alert anyone who is outdoors to seek shelter and find more information. The same networks are also used for other threats such as severe wind, hail, flooding, tsunamis, and industrial hazards.

The tornado siren you hear today descends directly from Cold War civil defense sirens. After the nuclear-attack mission faded, thousands of these sirens were repurposed across the United States "Tornado Alley" and the wider Midwest and South for severe-weather warning. That is why the two classic signals — a steady alert tone and a rising-and-falling attack wail — are still the backbone of tornado warning today.

Typical Pitch

Most sirens sound between about 500 and 900 Hz. Electronic sirens hold a precise tone; older mechanical sirens (like the Federal Thunderbolt) wail as the rotor speeds up and slows down.

Loudness

Roughly 120–135 dB at 100 feet — loud enough to be painful up close and to carry across open ground for about a mile per siren.

Duration

A real warning runs continuously for 3+ minutes (many systems re-sound until the threat passes). Short bursts usually mean a test, not a warning.

"Attack" (Wail) vs "Steady" (Alert) Patterns

Civil defense standardized two tornado-siren signals that are still used across North America. Use the buttons in the simulator above to hear each one:

Attack / Wail

A continuous tone that slowly slides up and down in pitch over a 4–6 second cycle, producing the unmistakable "wooooo—wooooo" wail. This is the signal most people picture when they think "tornado siren." In the simulator it is the default Tornado preset (Up-Down sweep, slow modulation).

Steady / Alert

A single, unwavering tone held at constant pitch for 3–5 minutes. Historically it meant "attention, monitor for information." Many communities today use a steady tone specifically for a tornado warning. Hear it with the Steady / Alert preset.

Why two patterns? A dual-signal system lets emergency managers convey urgency without words. The steady tone draws attention; the wailing attack tone signals maximum, immediate danger. Because meanings vary by county, you should always confirm what your local system's tones mean — and never rely on the siren alone.

Waveform of the Tornado Wail

Pitch
  900Hz     ╱‾‾‾╲            ╱‾‾‾╲
          ╱       ╲        ╱       ╲
  700Hz ╱           ╲    ╱           ╲
       ╱               ╲╱               ╲
  500Hz                                   ╲
        |----5s----|----5s----|----5s----|

Slow, continuous rise-and-fall "attack" wail
  • Fundamental: ~500–900 Hz, swept up and down
  • Wail cycle: one full rise-fall every ~4–6 seconds (0.15–0.25 Hz)
  • Sound pressure: 120–135 dB at 100 ft
  • Effective range: ~1 mile per siren in open terrain

When Do Tornado Sirens Test?

Test schedules are set locally, so they vary from town to town. Common patterns include:

  • First Wednesday of the month: a very common monthly test window, often around 10–11 a.m. or noon.
  • Weekly tests: many communities test every Saturday at noon (or another fixed weekday).
  • Monthly tests: some counties test on the first of the month or a set date.
  • Silent / growl tests: newer sirens can be tested electronically without a full sounding.

Weather cancels tests. Emergency managers almost always skip a scheduled test when severe weather is possible, so that a siren heard on a stormy day is never dismissed as "just the test." If you hear a full-length siren during threatening weather, treat it as real. Check your city or county emergency management website for the exact local schedule and tone meanings.

What To Do When You Hear a Tornado Siren

Outdoor warning sirens are designed to reach people who are outside — not to be heard clearly indoors. Treat any real siren as a prompt to act now:

  • Get in, get down, cover up. Move to a basement or storm shelter. If none is available, go to a small, windowless interior room on the lowest floor — a bathroom, closet, or hallway.
  • Get information immediately. Turn on a NOAA Weather Radio, check phone Wireless Emergency Alerts, or a local TV/radio broadcast to confirm the threat and location.
  • Protect your head. Use a mattress, blankets, or a bike/sports helmet to shield against flying debris, the leading cause of tornado injuries.
  • Never wait for the "all clear" siren. Many systems do not sound one. Stay sheltered until reliable sources say the warning has expired.
  • Do not rely on sirens alone. Have at least two ways to get warnings (phone alerts + weather radio), especially for nighttime tornadoes.

A Short History of the Outdoor Warning Siren

The modern tornado siren network was born from World War II and Cold War civil defense. Cities installed powerful mechanical sirens — most famously the Federal Signal Thunderbolt (1952) and the enormous, Hemi-V8-powered Chrysler Air-Raid Siren — to warn populations of aerial or nuclear attack. Standard signals were codified: a steady tone for "alert" and a wailing tone for "attack / take cover."

As the nuclear threat receded through the 1970s and 1980s, these sirens found a new, life-saving purpose: severe-weather warning, especially for tornadoes across the Great Plains and Midwest. Aging mechanical rotors were gradually replaced by electronic sirens that synthesize the same attack and alert patterns using an oscillator and a slow low-frequency modulation — essentially the same technique this simulator uses in your browser.

The stakes are real. The 2011 Joplin, Missouri tornado — 161 deaths — intensified national investment in outdoor warning coverage and in pairing sirens with phone-based Wireless Emergency Alerts, since sirens alone cannot reliably wake or reach everyone.

Frequently Asked Questions

What does a tornado siren sound like?

Either a steady "alert" tone or a rising-and-falling "attack" wail, sounded continuously for three or more minutes, typically between about 500 and 900 Hz. Press Tornado in the simulator above to hear the attack wail.

When are tornado sirens tested?

It is set locally: commonly the first Wednesday of the month, or weekly (often Saturday at noon). Tests are usually short and are cancelled during actual severe weather.

What should I do when I hear a tornado siren?

Go indoors immediately, shelter in a basement or interior room away from windows, protect your head, and confirm the threat with a weather radio or phone alert. Do not go outside to look.

How far can a tornado siren be heard?

About one mile in open terrain per siren (120–135 dB at 100 feet). Wind, rain, hills, and buildings reduce the range, so sirens are installed in overlapping networks.

Is this tornado siren simulator free?

Yes — it runs entirely in your browser at no cost, for education, demonstration, and creative use. It is not an emergency notification system.

Explore More Sirens

The tornado warning tone is part of a larger family of warning sounds. Explore related signals in our siren encyclopedia: