A State of Emergency can occur and be declared on National, State, County and City levels.
A state of emergency is a situation in which a government is empowered to perform actions or impose policies that it would normally not be permitted to undertake. A government can declare such a state during a disaster, civil unrest, or armed conflict. Such declarations alert citizens to change their normal behavior and orders government agencies to implement emergency plans.
A state governor or local mayor may declare a state of emergency within his or her jurisdiction. This is common at the state level in response to natural disasters. The Federal Emergency Management Agency (FEMA) maintains a system of assets, personnel and training to respond to such incidents.