Humanitarian crises and related complex emergencies caused by natural hazards or conflicts are marked by uncertainty. Disasters are extreme events mitigated through preparedness, response, and recovery. This article uses social complexity theory as a novel framework for deriving actionable insights on the onset T and severity S of disasters. Disaster distributions often show heavy tails, symptomatic of nonequilibrium dynamics, sometimes approximating a power law with critical or near‐critical exponent value of 2, not “normal” (bell‐shaped) or Gaussian equilibrium features. This theory‐based method is applicable to existing datasets. Policy implications include the usefulness of real‐time and anticipatory analytical strategies to support preparedness. © 2014 Wiley Periodicals, Inc. Complexity 19: 95–108, 2014