The ice storm of 1998 required extraordinary efforts from workers mobilized by the crisis. In order to evaluate workers' stress levels some months after the crisis, identify worst stressors and to assess the role of cognitive appraisal and work parameters in stress, a study of 870 ice storm workers from Hydro-Quebec was conducted according to types of job, areas, and types of assignment. Results indicated high stress levels in workers, associated with ice storm effort but not with job levels. Women appeared especially stressed, significantly more than men. Uncertainty and overload were the most cited worst ice storm stressors. Stress was found to be mediated by Impact and Uncertainty appraisal. Contact with victims, first line work, being oneself a victim were key factors. Results are discussed in light of current stress models and organisational psychology in the context of work during a natural disaster.