Answer
It is permissible to perform the Qadhaa of your Dhuhr Salaat after the Asr
Salaat till before sunset. However, a little before sunset, when the sun’s
rays lose their heat and become yellowish, Qadhaa Salaat becomes prohibited.
(Shaami vol.1 pg.375)
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai
FATWA DEPT.