“Emergency” means the actual or threatened existence of conditions of disaster or of extreme peril to the safety of persons and property within this City caused by such conditions as air pollution, fire, flood, storm, epidemic, riot, drought, sudden and severe energy shortage, plant or animal infestation or disease, the Governor’s warning of an earthquake or volcanic prediction, or an earthquake, or other conditions, including conditions resulting from war or imminent threat of war, but other than conditions resulting from a labor controversy, which conditions are likely to be beyond the control of the services, personnel, equipment and facilities of this City, requiring the combined forces of other political subdivisions to combat.