When does lightning present the greatest hazard to the crane and rigging personnel?

Lightning presents the greatest hazard to crane and rigging personnel during the presence of thunder and lightning. This is because these conditions indicate an active electrical storm, which greatly increases the risk of a lightning strike. The combination of thunder and visible lightning suggests that the storm is nearby and that the conditions are ripe for dangerous electrical activity.

During such weather, cranes, being tall structures, act as attractors for lightning strikes, putting both the equipment and personnel at risk. In addition to direct strikes, the associated winds and changes in atmospheric pressure during a storm can pose further hazards for crane operation and rigging safety.

While rain, cloudiness, or weather warnings can indicate the potential for storms or adverse conditions, the immediate risk is most accurately assessed when lightning and thunder are present, as they signal active electrical phenomena. Hence, recognizing this specific condition is crucial for ensuring the safety of personnel and equipment on site.