I agree with the others. Not too warm, especially for someone up north here, but might be too heavy ... especially if you are adding stabilizer to the T-shirts. That said, I had a friend in grad school who had exactly that quilt & it was no heavier than the purchased bedspread my mom has with tons of dense embroidery.
I think it all depends on how it's going to be used and the personal preferences of the recipient. Can you ask him if he thinks she'd prefer something akin to a weighted blanket or something lighter weight?