The short answer is: "no." Below ISA temps are NOT accounted for in the terrain clearance implied by given QNH-flown altitudes.
Yes, you do have to make your own corrections based on the table to which you allude.
Many exhaustive posts this topic in the PPRUNE archives by-the-way.
An excellent point to raise as the temps plunge. Merry Xmas, if applicable.
[ 25 December 2001: Message edited by: bizjet pilot ]</p>