Outdoor warning sirens are designed to warn those outside of threatening weather or some other type of emergency. You may or may not be able to hear a siren from within your home, especially when you are sleeping.  Also, sirens may become disabled by severe weather.

Sirens are activated primarily by city or county officials. Each city or county can establish its own guidelines for when to activate the siren, such as for severe thunderstorm warnings in addition to tornado warnings. Contact or visit the website of your city or county emergency management for outdoor siren policy.