What is essential for planning rigging for a specific lift?

The knowledge of the load's weight and dimensions is crucial for planning rigging for a specific lift because this information directly affects the selection of rigging equipment, such as slings, shackles, and hoists. Understanding the weight helps in determining whether the lifting equipment can safely carry the load, while knowing the dimensions allows for adequate spacing and clearance during the lift. Proper calculations based on this data help ensure safety and efficiency during the operation.

While trained personnel and weather conditions are factors that also play important roles in rigging and lifting operations, they do not directly relate to the technical aspects of the load itself as weight and dimensions do. Trained personnel ensure that safe practices are followed, and weather conditions can impact the safety of the lift, but neither can substitute for the fundamental requirement of understanding the load's characteristics in the planning phase. Therefore, option B stands as the most essential component for planning rigging effectively.