As soon as this cold spell is over, a good time to re-seed the patches. Lightly rake the patches over to remove the dead thatch and if you water well, mix the seed with a little fine compost and then cover with clear plastic the patches will recover before you know it.

The only solution I can think of is to plant new seed. Square off the patches for convenience. Dig out about an inch of top soil and replace with new top soil. Sow the new fescue grass blend seed mix. Water daily. Don't sow the seed too thickly; it will naturally thicken up on its own. Should take two weeks.