FEMA and the National Weather Service are looking out for you. How so? They're joining up to launch the Wireless Emergency Alert System, which is described as a free SMS system that will text users connected to cell towers in areas that are being nailed with storms or other disasters. The idea here is to broadcast them to all devices within range. It's engineered to cover around 97% of the nation, but it's just now being rolled out across operators. Both Sprint and Verizon (the two largest CDMA carriers in the States) are both primed and ready, but there's no word yet on some of the smaller, regional carriers nor AT&T / T-Mobile USA.
It's worth noting that not all phones will work; those of the older variety may have issues. It's still a great start in using existing cell towers to provide public announcements, and hopefully it'll be spread further to keep people in the know when bad times strike.