The reduction in current rating of cables installed in direct sunlight can be significant.

Cable Pro has selections for standard configurations which accounts for direct sunlight.

Another method is to use the Derating Wizard inside the software to apply a derating factor for the temperature increase above ambient.

Section of Standard AS/NZS 3000:2018 suggests applying a derating factor for a temperature 20 deg.C. higher than the ambient temperature.

For example, see below the ambient temperature was increased from 40 deg.C. to 60 deg.C. which creates a derating factor of 0.6 (or a 40 % reduction in the cable current rating only due to direct sunlight exposure).