Sirens are a public warning system used by many communities across the United States to alert people to impending weather dangers. They are designed to warn the public outdoors, but may also be heard inside some homes and buildings (especially those built in brick or concrete).
The sounds produced by sirens vary widely from one region to the next. They can include a variety of tones, such as an "alert" tone that lasts for three minutes, and a "attack" tone that varies from a low roar to a high rumble.
When a tornado is near, there is usually heavy rain, or hail that can uproot trees or break windows. There will also be dead calm or a fast, intense wind shift.
A loud, continuous roar or rumble that doesn't fade after a few seconds like thunder.
A police siren is typically used for a general emergency, such as a bomb threat or an approaching tornado. A tornado siren is more common and is often a public safety tool.
If you hear a tornado siren, it is important to take cover immediately and listen to the local media for information on the storm. Taking cover is the most important thing you can do to protect yourself and your loved ones, especially if you are outside.