All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is forbidden to perform the prayer when the sun is at its meridian and this is just before the starting time of Thuhr. When the time of Thuhr starts, it is then permissible to perform the supererogatory prayer.
However, on Friday it is permissible to perform the supererogatory prayer at any time and even before the sun is at its meridian; for more details, please refer to Fatwas 90213 and 82753 where we clarified that there is no confirmed Sunnah prayer before the Friday prayer, contrary to what the questioner may think.