Time is of the essence during a tornado. If you're sleeping or otherwise occupied as a storm begins to build, you may have no idea of the danger you and your family are in.
NOAA (National Oceanic Atmospheric Association) Weather Radios send out bulletins and alerts 24 hours a day. The radios can be programmed to emit only information pertaining to your community. In short, you may hear nothing out of the radio for months, but you'll be alerted to find shelter when it matters most. The Federal Emergency Management Agency recommends having a weather radio as part of your disaster kit. Weather radios are battery-operated, so if you lose electricity, you'll still receive the necessary information.