The ambient temperature is one of the conditions specified in the headings of the tables. For example, Table 310.15(B)(16)  applies to conductors in a 86° Fahrenheit or 30° Celsius ambient temperature.

If the actual ambient is different, then “correction factors” need to be applied to account for the difference in considering this determinant.

Excerpt from Table 310.15(B)(16) highlighting the heading showing the ambient temperature the allowable ampacity is based on. A correction factor from Table 310.15(B)(2)(a) must be applied if the ambient temperature is different from 30 degrees C.