Every two seconds someone in America needs blood. When a disaster strikes, the demand for blood is usually so high that it necessitates an urgent appeal for donors. If you can, become a regular donor but especially in an emergency situation, giving blood is one of the very best ways to help others in need.
The Red Cross increases their hours of operation before a known disaster, like a Hurricane, and maintains them, whenever possible, after an event in addition to using mobile units for local blood drives. See their website for more detail!