The Incident  Period is the time span during which the  disaster-causing incident occurs. This period varies in length, depending on  the type of incident. For example, the incident period for a flood event  could be several weeks, because the water has to crest and recede; while the  incident period for a tornado would be one day, because the damage occurs in  a matter of minutes. Damage that occurs during the incident period, or damage  that is the direct result of events that occurred during the incident period,  is eligible. Protective measures and other preparation activities performed  within a reasonable and justified time in advance of the incident period may  also be eligible. The incident period will be established by FEMA in the  FEMA-State Agreement.
   Reference: Public Assistance Guide, FEMA 322,  pages 29-30