Which of the following is NOT a factor in determining the actual lift capacity?

The choice indicating surface weather conditions as a factor that is NOT involved in determining the actual lift capacity is accurate because weather conditions typically do not directly affect the mechanical capabilities or lift capacity of equipment. While weather can influence operational safety and may require adjustments to procedures (such as securing loads in high winds or avoiding operations during heavy rain), it does not change the actual lift capacity as defined by manufacturer specifications or the physics involved in lifting.

When assessing lift capacity, factors like truck stability are critical as they directly relate to how safely and effectively a load can be lifted and moved without tipping or toppling. Manufacturer's lifting limitations are essential because they specify the maximum loads that each piece of equipment can handle under ideal conditions. Similarly, the position of the boom in relation to the load matters significantly, as it affects leverage and the distribution of weight, thus influencing the effective lift capability.

In summary, while all these factors are vital to considerations of lift operations, surface weather conditions do not alter the mechanical lifting capacity of the equipment itself, making it the correct answer to the question.