Weather radios have been the de facto means of weather emergency communication for decades, but the National Weather Service is bringing its warnings into the 21st Century.
Starting in May, the agency will begin texting tornado, flash flood and other warnings to wireless users in the affected county. There is no need to sign up for the alerts, but not all cell phones are capable of receiving them.
The alerts will have special tones and vibrations that will be repeated twice, and they will display messages of up to 90 characters. Like television-based severe weather alerts, the text alerts will be distributed based on a user's distance from local cell towers; cell phones' locations will not be tracked.
The system will distribute severe weather alerts, AMBER alerts, and presidential alerts during national emergencies. It will be possible to opt out of all the alerts except the presidential alerts.
Here are the National Weather Service's answers to frequently asked questions about the alerts, and here is information from CTIA-The Wireless Organization on cell phones and carriers capable of distributing the alerts.