What Does "State of Emergency" Really Mean?
The answer varies a bit from state to state, but basically, declaring a state of emergency gives the governor and his emergency management team a bit of extra latitude to deal with a situation quickly and with maximum coordination. Most of these powers are fairly straightforward; the governor can close state offices, deploy the National Guard and other emergency responders, and make evacuation recommendations.
Other powers are specific to a certain situation. For example, in a blizzard a governor can impose travel restrictions to clear roads for snowplows and other emergency vehicles.
Calling in the Feds
If a disaster is so severe that state and local governments don’t have the cash or the logistical ability to adequately respond, the governor can ask for a declaration of a federal emergency. In this case, FEMA does a preliminary damage assessment to help determine whether the governor should petition the President for a federal emergency declaration.
When the declaration from the President comes through, state and local governments can get funding and logistical help from the federal government. What makes a crisis a federal emergency? The list is pretty broad, but FEMA shares some of the criteria on its website.